Many of the resources listed below are from Will Richardson's most recent publication, Blogs, Wikis, Podcasts and Other Powerful Web Tools for Classrooms. Some explanations are from Wikipedia.

From David Warlick's "Educator's Guide to Blogging"

WEBLOGS (BLOGS) - websites that allow an author to publish instantly on the Internet. They can be interactive, allowing teachers and students to begin conversations or add to the information published there. Blog/WebLog: a web page containing brief, chronologically arranged items of information. A blog can take the form of a diary, journal, what's new page, or links to other web sites. (Peter Scott, Internet Librarian 2001)
Weblogs provide a communication space that teachers can utilize with students whenever there is a curriculum need to develop writing, share ideas and reflect on work being undertaken in the classroom. (Weblogs in the Classroom)

WIKIS - a collaborative webspace where anyone can add content or edit that which has already been published.
Wikis provide unique collaborative opportunities for education. Combining freely accessible information, rapid feedback, simplified HTML, and access by multiple editors, wikis are being rapidly adopted as an innovative way of constructing knowledge. (Encyclopedia of Educational Technology)
Teachers and students can use password protected wikis to share ideas to create a dynamic digital information resource.

RSS (RICH SITE SUMMARY) - RSS is a technology that allows educators to subscribe to "feeds" of the content that is created on the Internet. Rather than searching the Internet for content, RSS brings the content to the subscriber. RSS lets us read and connect with what others write. (Will Richardson)

AGGREGATORS - collects and organizes the content generated in an RSS feed. An RSS Aggregator collects and organizes the content generated via the RSS feed. (Will Richardson) Collective feeds can be combined to keep related work together such as individual student's classroom Weblogs.

SOCIAL BOOKMARKING - Online bookmarking services allow you to save links, annotate them with unique key words "tags" to organize them, and share them with the world. These services take all of the entries that are tagged the same way and connect them, and then connect all of the people who posted those links in the first place. Social bookmarking connects us with what others read and consequently allows us to tap into the work of others to support out own learning. (Will Richardson)

SOCIAL NETWORKING (NINGS) - an online platform for creating social websites and social networks. The websites running on its service are built in standard PHP and the platform itself is built in Java.

AUDIO/VIDEO-CASTING (PODCASTS/VODCASTS) - voice and video files distributed via the Internet.
Digital voice and video files can be produced and published on the Internet allowing students to communicate in a number of different media. RSS allows people to subscribe to podcasts and videoblogs.
  • Podcasts are radio shows that are downloaded over the Internet; all that is required to do this is a digital audi recorder that can create an MP3 file, server space to host the file, a blog, and a message.
  • A videoblog, or vlog, is a Web log (blog) that uses video rather than text or audio as its primary media source; videoblogs are usually accompanied by text or still images.

MASHUPS - a Mashup is a combination of one or more data sources to create a unified interface and experience.
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ONLINE PHOTO GALLERIES - Students and teachers can include digital images in the content they create and publish to the Web. Flickr is probably the best online photo management and sharing tool. Flickr allows users to add tags and notes to organize their photos and other users can make comments about their work. When publishing images to the Web, privacy options can be selected to make viewing and sharing access restricted to your class alone.

APPS & GADGETS & WIDGETS - applications that will in some way increase productivity and/or reduce time taken for specific tasks.
This must be what Inspector Gadget would say if he had Yahoo! Widgets–formerly known as Konfabulator–installed on his system. But, alas! It’s Google that uses the term “gadgets” to call its, err, widgets, with its own collection of applets called Google Gadgets, part of the Google Desktop Search.
Somewhat confusing, eh?