I read about this wiki on Library Stuff. Wiki's are great tools to utilize for several reasons. First, it can be used on your website by your patrons. For example, you can create a wiki on the best books to read and have your patrons make contributions to it. Secondly, it is a great tool for project management. If your staff needs a inexpensive tool to track that critical project, wiki's allow for easy interaction between the project team because anyone can contribute and edit a wiki page. Finally, if you are working on a publication with a group of people from different locations, a wiki allows you to centralize the document so tracking versions is not so difficult.
We plan to start using wikis here at NTRLS in the near future. We have discoverd PBwiki which is a free for the basic service. Keep an eye out.