What's tomorrow's YouTube? The Web's next breakout hit may be one of these innovative, useful, and fun new sites.

Think that all of the great Web sites have already been invented? Think again. The Internet is evolving in new and inventive ways thanks to mashups that pull data from all over the Web and to AJAX-based interfaces that give sites the same degree of interactivity and responsiveness that desktop apps possess.

To keep you ahead of the curve, we've rounded up 25 innovative Web sites and services that are well worth watching. Some of them help you design your own personalized Web site mashups; others enable you to create video mixes, build wikis, share personal obsessions, and more. But take note: A number of these sites are works in progress, and user-generated sites depend on developing a critical mass of content, which doesn't happen right away. With that in mind, check out the following dot-com destinations. One of them may become the next big Web hit.

Popfly

If you haven't already discovered the world of mashups, Microsoft's Popfly is a good place to start. Mashups combine multiple Web-based sites or applications to produce all sorts of useful things, such as an overlay of traffic information over Google Maps. With Popfly, you can create your own mashups--and you don't have to know a lick of code to do it. Just drag prefab building blocks, connect them, and you have an instant mashup that you can add to an existing Web page or turn into its own site. For example, you can easily produce a mashup that grabs pictures from a site like Flickr and then displays them in a rotating cube.

Yahoo Pipes

Like Popfly, Yahoo Pipes lets you create your own mashups or "pipes." As with Popfly, you drag and drop prebuilt modules, and then create connections between them. But Yahoo Pipes is much harder to use than Popfly, and the way to go about building your own mashup isn't always obvious. But if you're willing to do some digging and learning, you can build very useful stuff, such as a mashup that uses Yahoo maps to show the locations of all apartments for rent in a certain neighborhood.

BuzzDash

Are foreign movies better watched with subtitles or with dubbed dialog? Is it okay to cry at work? Who is the best center fielder of all time--Willie Mays, Joe DiMaggio, Mickey Mantle, Ty Cobb, or Ken Griffey, Jr.?
If these are the kinds of issues that keep you awake at night, we have a Web site for you. BuzzDash lets you participate in, comment on, and see the results of numerous quick opinion polls. The polls are organized by topic, such as movies, football, and politicians; and if you have a burning question you want answered, you can create your own survey.

Wayfaring

If you're obsessed with cartography, wander over to Wayfaring.com. Here you can easily create personalized maps for a walking tour of London, say, or a wine-tasting trip through Napa or a pub crawl through Seattle. The site provides the tools you'll need to build annotated maps--complete with descriptions, Web links, and photos of your favorite stops--and then post them for others to view and discuss. It's fun to check out the maps other users have created. One of my favorites: a map of shipwrecks in the Great Lakes, including links to Web sites that discuss each wreck.

CircleUp

Anyone who has ever tried to organize an event--or to get a group of people to respond to a simple question like "Who can drive the kids to Little League this week?"--knows how tough it is to filter and organize the answers into coherent, usable form. That's where CircleUp comes in handy. Use this site to send an e-mail or instant message to a group of people; then wait for it to return a consolidated summary of responses to you. It's simple, it's free, and it will liberate you from the recurring feeling that you're herding cats whenever you try to coordinate an activity involving more than two people.

Pageflakes

The Web is just as chaotic as the world--but Pageflakes can organize both of them for you. This super-customizable version of a home page enables you to pick the news and information feeds you want to read, and to specify the "flakes," or applets, you want to include. Flakes let you add all sorts of cool stuff to your page--movie times, to-do lists, a notepad, e-mail, a horoscope--even sudoku or a personal blog. If you're looking for one-stop browsing, this is it.

SpockIf

you spend more time than you should googling folks, you need to check out Spock.com, a search engine designed to dig up information about people. Start by typing in a name, or a search term that describe a group of people--for example, Motown Singer, or Rastafarians. The site then searches through various social networking sites such as MySpace and Friendster, along with more-general Web sites, and reports on what it finds.

For many searches, you'll get multiple categories of links. For instance, type in Barack Obama, and you'll get groupings like 'Democrat', 'Senator', and '2008 Presidential Candidate'. Click any link, and you'll find pages related to both Obama and the larger category. There are also links to photographs, tags, Obama's Wikipedia entry, his Senate site, and so on. Spock is currently in beta form (its public launch is scheduled for sometime before September), and at the moment you need an invitation to gain access to it, but with luck you can wangle one by filling out the form on the site.

Swivel

Data and graph fanatics, you have a home. Swivel, holds a mind-boggling array of charts and graphs--from a line graph illustrating the relationship between wine consumption and crime in the United States over the past 30 years to a pie chart showing the percentage breakdown of bird flu cases in 14 Asian countries. But the site's most outstanding feature is its ability to integrate different charts containing seemingly unrelated data. Want to compare the national murder rate to the cost of a first-class stamp, or to total hours of media use in U.S. households, over the same period of time? Now you can.

Clipmarks

The Internet is the best research tool in existence. That's the good news--and the bad news. Though finding information online is easy, keeping track of it all can be tough. Most people end up copying and pasting information from Web sites, printing it out, or bookmarking pages--with no good way to keep it all organized or find what they want fast.

Clipmarks solves the problem neatly by installing a toolbar that hitches on to Internet Explorer or Firefox. As you surf the Web, use the Clipmarks toolbar to clip and save sections of a page--text, graphics, and even YouTube videos. Clipping something automatically archives it under your Clipmarks profile, though you can also save it directly to your blog or send it via e-mail. You can even share your clip collections, or look at archives that other users have assembled.

OpenDNS

One reason the Web sometimes feels poky, even when you use broadband, is the Internet's Domain Name System. When you type a URL (such as www.pcworld.com) into your browser, DNS servers must translate that alphanumeric information into a numeric IP address (such as 70.42.185.10) that Web servers and your PC can understand. Typically your ISP's DNS servers handle the translation work.

But OpenDNS speeds up the translation (called "name resolution") by handling the process on its own high-speed DNS servers. The service includes other cool time-savers, as well, such as the ability to create keyboard shortcuts. For example, instead of typing www.pcworld.com each time, you might arrange to type in the letter p and jump immediately to your favorite online destination.

Trulia

There are plenty of real-estate sites on the Web, but this one comes with a twist. By combining social networking with mapping and search technology, Trulia gives you a high-tech way to find the home of your dreams. Use the different sliders and checkboxes to focus your search (price, square footage, and the all-important number of bathrooms), and Trulia will display qualifying homes that are for sale in the specified area, overlaid on a map. The site includes useful, city-specific real estate guides containing additional data on average home sale prices, most popular neighborhoods, crime statistics, and the like.

The Trulia Voices section hooks you up with other people to discuss neighborhoods, housing issues, or real estate in general. Trulia is relatively new, so that section is as yet quite sparse. But if the site gains traction, Trulia Voices may prove to be the most useful tool of all.
Tip: To view some cool time-lapse maps showing how an area (such as Las Vegas) has developed over time, hop to Trulia Hindsight.

PopURLs

If you're an information hound, you probably spend lots of time jumping from Digg to Del.icio.us to YouTube to Fark to Google News to anything-dot-com. With PopURLs, you no longer need to waste time hopping around the Internet. An aggregator of all things informative, PopURLs features massive lists of headlines, videos, blogs, and content from all of those sites, as well as plenty of others.

One nice bonus is that you can search some of the sites--Del.icio.us, Flickr, and Wikipedia, among others--straight from PopURLs. It's also easy to tweak the way PopURLs looks and works, too, including customizing the layout of the feeds so you can put the ones you view most regularly on top. The scrapbook is a particularly useful feature; just click the 'Add to Scrapbook' button next to any headline, and PopURLs will save it (and up to 19 other favorite items).

Goowy

For several years, observers have speculated that the Internet will become, in essence, a vast operating system, with applications built on top of it. To a great extent, that's the premise underlying Goowy. Create an account, and you can start building your own desktop, with applications for e-mail, contacts, instant messaging, file management, and more. You can also add prebuilt widgets, called "minis," to your desktop, for news, stocks, weather, and other tidbits of information.

Don't expect the site to replace your desktop at this point: Goowy lacks full-blown applications and doesn't access your hard drive. Still, it's a glimpse into what may be the future of the Internet.

BlogBackup

OnlineIf you have a blog and you aren't sure that your blog provider will always have a backup in case of a crash, head over to BlogBackupOnline pronto. The site is straightforward: Log in, enter information about your blog, and the site diligently backs it up every day (provided that you use one of the 11 supported blogging services--Blogger, Friendster, LiveJournal, Movable Type, Multiply, Serendipity, Terapad, TypePad, Vox, Windows Live Space, or WordPress). The site is also a great tool if you ever decide to move your blog from one platform to another. After you've backed up your blog, BlogBackupOnline can bring all of your old entries into the new service.

Ma.gnolia

If you're a fan of the social bookmarking site Del.i.cio.us but wish that it were a little more social--and a little less geeky--check out Ma.gnolia. As with Del.icio.us, you can save and share bookmarks and tags. But Ma.gnolia presents a far more appealing design, and it has a few nice extra talents, such as the ability to let you save snapshots of your favorite pages.
Ma.gnolia excels on the social networking front. You can join groups, share bookmarks, and browse groups and discussions for more bookmarks on topics that fascinate you. If you're strictly interested in bookmarking and tagging, Del.i.cio.us remains the best place to go. But if you want to share your findings with others, Ma.gnolia is worth a taste.

Yodio

Of course your friends and family want to see all of your pictures from your Venetian vacation--but wouldn't it be better if they could also hear your voice, telling you cool details about what they're looking at, or narrating a story regarding some gondola hijinks?

Yodio lets you combine photos with sound files to create an audio postcard. To make a recording, call a special Yodio phone number and start talking (or you can record your own MP3 file and upload it). Once you've transferred photos to the site, you can add sound and publish your postcard on the Web for others to admire. The site also has a scheme for making money from your productions, though we wouldn't bet the farm on it.

Meebo Rooms

You may have heard about Meebo, the Web-based instant messaging program that lets you communicate with people over various IM services, such as AOL Instant Messenger and Yahoo. (See our review of Meebo.)

Well equally cool is Meebo's newest launch, Meebo Rooms, which lets you participate in multimedia chats. You'll find chat rooms on everything from sports to SpongeBob Squarepants, and the rooms support videos and photos that you can discuss with fellow fans. If you can't find a topic you're interested in, simply create a new room and post visuals for others to discuss. You can even embed rooms into your site or blog, and use them to lure people to your own Web destination.

Squidoo

Got an obsession or special passion you want to convey to the world? Squidoo is your ticket. Using the site's simple tools, you can build a "lens" (aka, a Web page) that includes information on any topic that's close to your heart, whether it's cats or Kafka.

A lens can be quite different from a blog. With lenses, you share links to resources, book recommendations, YouTube videos, Flickr photos, eBay auction items, and other cool Web content related to a single subject. Even if you don't build your own lens, the site is worth visiting to see what others have done. You can learn a lot more about lemonade or laptop bags than you ever thought possible.

SplashCast

For anyone who has ever dreamed of becoming a broadcast mogul, here's a quick (and free) way to get a taste of what it might be like. SplashCast lets you create your own streaming media channel that combines video, music, photos, text, narration, and RSS feeds. A wizard walks you through the steps of building your channel. Start by uploading media files from your hard drive, or point to files on other sites. Add captions, commentary, and RSS feeds, and your channel is ready to go. Once you're done finessing your channel, you can send it to friends and family, or syndicate it to blogs and social networking sites. So far, there's no way for you to make money from your channels, but the site plans to start a revenue-sharing model.

Eyespot

To create a video all you have to do is point your cell phone, digital camera, or camcorder at something, press a button, and stay focused. The result: an instant movie. What's not so easy, though, is organizing, editing, and combining your video clips to create something aesthetically pleasing. Eyespot simplifies this process. Upload your videos to the site, and then use its tools to crop and mix them either with other clips you supply or with free video from the site. You can even add effects, transitions, and titles before publishing your video mix for the world to see.

Approver.com

Anyone who has collaborated with multiple people on a document knows the true meaning of frustration. You have to distribute the file to the entire group, convince every person to review it by a certain date and time, and get them all to sign off on it. Approver.com lowers the pain quotient considerably. Upload the document you want to track, and the site routes it to everyone who needs to see it. It also lets you set deadlines for reviewing the document, and keep track of approvals and comments. Approver.com works with a number of apps, including Microsoft Office, Adobe PDF, and Open Office; alternatively, you can use the site to create documents, and have your colleagues read them online.

Pbwiki

Though the whole world seems to know about Wikipedia these days, many people and organizations don't realize how useful it can be to build their own wiki. In business settings, it's an ideal way to share information within a group. For individuals, it's perfect for planning a get-together, organizing a fan club, or sharing memories with family members. Pbwiki makes creating miniature versions of Wikipedia a breeze. The site's simple, Web-based tools are perfect for building a wiki--you don't need to have any HTML know-how--and getting others in on the editing action.

MyPunchbowl

Planning a party, but unsure of what date works best for your friends? MyPunchbowl is basically Evite with a little extra kick. Like any self-respecting online invitation site, MyPunchbowl lets you create party invitations and then track who's coming, who's not, and who has yet to respond. But the site also enables you to send pick-a-date e-mail messages to see which day works best for people, set up message boards (useful for organizing things like who's bringing the vino), and produce a map of the shindig's location using Google Maps. You can also create an after-party message board where people can share comments, photos, and videos--if, um, appropriate.

Picnik

You probably have hundreds or thousands of digital photos on your PC. And a lot of those photos would probably benefit from a little tweaking. But that doesn't mean that you have to download and install photo editing software. Picnik supplies a nice suite of tools for editing photos online. All you have to do is upload your photos, or have Picnik grab them from a site like Flickr (which doesn't have editing features), and then get to work. Picnik offers tools aplenty for performing simple editing--cleaning up red-eye or resizing photos, say--as well as doing more-extensive work, such as changing the exposure, fixing a color cast, or applying special effects.

Quintura

Quintura provides a new way for you to search for things on the Internet. When you enter a search term, Quintura returns an ordinary list of results on the right-hand side, while on the left it offers a visual map (or "cloud") of related terms. Click any of these words, and the list of results changes to encompass the new term as well, which can help you narrow your search. The process may sound clunky, but it's surprisingly effective.