Wikis are web pages that can be edited by anyone who has access to them. This allows for collaboration and communication between participants. The most widely known use of the Wiki format is Wikipedia, the online encyclopedia that is continually edited by thousands of people around the world.
A wiki is more than a web page, it's a place to collaborate and share learning. This video from Common Craft's Lee Lefever explains it best:

The service used to create this wiki is Wikispaces, a wonderful tool with an easy to use interface, that is very appealing to teachers and students. Wikispaces gives educators the ability to choose protected, private, ad-free spaces for free. You can get a free educator Wikispace. Wikispaces has quick tours to help you get started using your wiki.

Other free wiki hosts are PBWorks and WetPaint.

Wiki Resources

Because of the collaborative nature of wikis, many educators have worked together to create rich resources on using wikis in the classroom.
Educational Wikis is a comprehensive wikispace of resources, and is open for editing by all.

To learn more how to use wikis in the classroom, visit these outstanding presentations on Wikis at the K-12 Online Conference:
  • An introduction to wikis, called Wiki While You Work by Mark Wagner, is a great way to learn about wikis and how they can be used in the classroom.
  • Wiki Collaboration Across the Curriculum by Vicki Davis. Vicki is well known for her outstanding work with students using Wikis at Westwood Wiki. This presentation includes an very informative video on how to use wikis, as well as supporting documents that can be used in the classroom.

Sample Education Wikis

The Flat Classroom Wiki An exemplary classroom project between students in many countries who come together to collaborate on a project.
Arbor Heights Elementary School Web Page by Mark Ahlness
Armstrong US History Site - from a school in Korea
Westwood Wiki by secondary students at Westwood High School by Vicki Davis

Additional Resources on WIkis

My bookmarked resources on with the tag "wiki"