The variety of wikis are pretty amazing. I really like how some of the libraries on the list are using their wikis for pathfinders and book reviews. I appreciate that wikis are free (for teachers) and also accessible for lots of people. Nothing like information access. And wikis take things to the next level. Not only are they accessible, but they are edit-able. It is great to encourage participation from the community. Another positive feature of wikis is that that they can be whatever you want them to be. And they are flexible in terms of content. You can post pictures, documents, links, etc.
In my school community, the Physiology teacher is using a wiki for collaborative note-taking. I have brainstormed with teachers about how they can use wiki technology in the classroom. So far, no one has jumped on the band wagon. Although for the library group I belong to Bay Area Independent School Libraries (BAISL), we are using a wiki to collaboratively edit position papers that we publish. I could see school libraries using a wiki to post procedures of how to access databases or the catalog. It would be great to have a whole "how-to in the HNHS library" where students could go when they had a question.