I recently purchased Mader's book "Wiki in Education" - it contains 10 case studies written by educators who used wikis in their classrooms, which Mader (the wiki consultant behind http://www.ikiw.org) then edited into a book. I'm not finished with it, but so far it's got some great information, and I'd highly recommend it. There's a link to the book on Stewart's blog: http://www.ikiw.org