Wikis are websites that use special software to allow users to create or edit web pages. They ususally have a table of contents, pages that lead to subpages. Wikipedia is the largest one, but there are many others.
Over the last couple of years I have looked at Wikipedia and have gone to never using it to using it as a tool for basic information. It is also a great way to show students how the Internet has its own point of view and how web sites can developed.
I went to a sample page set up for the North Texas 23 participants. It was very easy to add pages and pictures. The process is much like other web applications and there wasn't much of a learning curve.
I would love to have some of our students create an entry in Wikipedia for our school. I think this would be a great experience for them.