Here is a collection of outstanding Wiki educational applications

Dean Shareski’s Wiki
Very nice resource on Read/Write Web tools, including wikis.

Dean Shareski's Digital Storytelling Wiki
An example of a wiki to drive professional development.

Will Richardson's Weblogg-ed Presentation Links Wiki
Comprehensive Read/Write Web resources

Bud Hunt’s Wiki
Created by Colorado teacher Bud Hunt and many educator-collaborators.

David Warlick’s Presentation Handout Wiki
A wiki designed to support the presentations of education guru David Warlick

DG Summit Wiki
Supports a two-day staff development project on Read/Write Web methodologies; includes participants’ blogs, session podcasts, and handouts.

Educational Blogging Wiki
Supports the educational uses of blogs and contains links to student and teacher blogs.

High School Online Collaborative Writing
Features the collaborative writing of various high school students.

Library Success: A Best Practice Wiki
A collection of smart practices for libraries and the issues that impact them.

Mrs. Davis’ Westwood Schools Wiki
An online space for Westwood schools’ students that includes a variety of student projects, including an insightful analysis of Web 2.0 tools.

PodcasterCon wiki
Supports collaborative pre-conference planning for PodcasterCon 2006, an event for learning about podcasting, and hosts content about each session that participants can add to.

Swarmsketch
Just for fun: This site allows you to contribute a single line to a drawing, and then vote for the inclusion of other lines in the drawing.

Wikibooks
Collection of textbooks that can be edited by anyone.

Wikiville
A wiki where students can build stories about where they live.