The folks at Eastwick Communications are running a series of blog posts about wiki-based collaboration, called 33 Wikis.
33 Wikis: Each day -- for 33 days -- we look at one wiki and briefly describe what the wiki is for, why we like it, and what we all can learn from it. If you want to nominate a wiki, please let us know. On day 34 we will post a public wiki featuring info on all nominees.
They're reviewed some interesting applications - tech developers, political organizing, autism resources, legal resources, product user communities and others. These examples demonstrate a lot about how wikis can be valuable.