The wiki concept is interesting and I am not sure right now what separates it from a blog. The uses are varied from using it strictly as a blog to using it as a web page for a school
http://arborheights.wikispaces.com . This is a great easy way to update a school website without waiting for the webmaster to do all the updates. There is immediate news about school events. This way many people can help keep the school site current. There is also the using it as a teaching tool for one specific task. The wiki for the study of the book
Turn Homeward Hannalee is well done and obviously done by students, which makes it useful as a study guide and an assessment
http://wiki.woodward.edu/hannalee/doku.php . Since my class reads that book, it is particularly relevant. I can see how creating a wiki would make for a great wrap-up for a class book.
In the wiki,
http://www.gkbledsoe.com/articles/process/writing_prompt_generator.html, there was a page to help students think of stories to write, using prompts. That was fascinating. Since it was written by students it was very user friendly. However, the wiki at the "coolcat teacher"
http://westwood.wikispaces.com/Web+2.0 most interested me right now. I have a scholastic class homepage and find it cumbersome. I have been looking for another way to post assignments and class news online that is easily accessible to parents and students. This looks like it may work well. I like the idea of using wikis for book collaboration and a class web site.
I did not find things that I would change about the wikis I read, although some did not fit the capabilities of my students. So while I would not use them as extensively as some that I read, there is a place for wikis in my classroom.