Web 2.0
For a collaboratively produced, Web 2.0ish explanation of Web 2.0, visit the Wikipedia entry.
O'Reilly network (publishers of many tech books) has a longer, more critical article on Web 2.0.
To find out more about the philosophy behind community-driven, user-generated content, see James Surowiecki's book, The Wisdom of Crowds, or visit the Wikipedia entry/summary.
Take a look at directories such as Go2Web20.net or ProgrammableWeb for many more examples of Web 2.0 sites and applications.
The term "Web 2.0" refers to new web-based applications and/or networks that share certain characteristics. Most Web 2.0 applications aren't downloaded to a user's private computer, but instead they're used directly on the web; users can update content and interact in a seemingly instant way. Web 2.0 applications depend and thrive on community-driven collaboration and input, often referred to as 'user-created' or 'user-generated' content. Content can range from simple textual posts (events, comments, blog posting, etc) to multimedia such as digital audio, video, interactive presentations and other content.
Aggregators
Aggregators can sort, search, and even re-appropriate blog content. With an aggregator, users can stop visiting several individual blogs and websites, and instead access and read everything in one searchable, modifiable place. Read more about aggregators here.
Digital Image and/or Video Sharing 
Several Web 2.0 sites strive to share digital content such as photographs and video in a way continually generates connections with other users interested in the same content. Many sites promote themselves as being very user-friendly in terms of uploading images and/or video, making these kinds of sites attractive options for distributing digital resources. CIT currently has pages on the following digital image/video sharing tools:
Geomapping/Geospatial Tools
Web-based mapping tools have increasingly become useful for much more than getting directions. Advances in tools like Google Maps demonstrates the importance and usefulness of maps as a tool for visualizing and comparing several forms of data. Further advances in geospatial tools like Google Earth make it possible to observe and compare large collections of satellite imagery, enhanced with specialized tools and customization capabilities.Mashups
What happens when the content from one site collides with an application on another site? Theses kinds of sites/applications are called "mashups". Read more about mashups here.
Social Bookmarking
Social bookmarking sites attempt to build communities of users based on their decision to link to, cite, and otherwise reference specific websites, journals, and other resources. CIT currently has information on perhaps the most popular social bookmarking site/tool:
Social Networks
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Social networks (or social networking sites) allow users to create and/or join networks of friends, colleagues, or others with similar interests. Social networks focus on common pop culture interests (MySpace), common affiliations such as colleges/universities (Facebook started this way), or professional interests (LinkedIn). Social networking sites generally offer a variety of tools for customization and individualization, as well as several tools for communicating with those joined to the network (including file-sharing, instant messaging, cell phone text integration, message board posting, etc). CIT has more information available on the following social networking sites:
Virtual Worlds
Virtual worlds are web-based three-dimensional environments that can be explored and interacted with in a way similar to 3D videogames. Several education and business presences (including UNC, IBM, Coca-Cola, etc) have appeared in the virtual world Second Life, making it the most popular example of a virtual world and the kind of community it generates.
