Used in the right way, I am a big believer in using wikis and requiring students to participate more fully in the design and content of some of my courses in new media technology and emerging web applications. I have used several flavors including MediaWiki, Wetpaint, PBWiki, MindTouch Deki. Requires some orientation for students to get them comfortable with the interface and toolset but well worth it. Don Tapscott's book Wikinomics changed everything for me.