InformationWeek has a pretty complete primer about using wikis in business that's definitely worth reading, along with links to examples of companies using wikis,including Kodak, Cingular, and Disney.
But one place where I tend to disagree with the article is when it describes what wikis are good for.
"Wikis are structurally capable of handling conversation, but it is not their forte; instead, wikis excel at collaboration. They are intended to maintain a series of unique documents as their content evolves and to provide an organic means of organizing that information."
I think this is in part true, but I think that the bigger issue is that facts aren't always facts. Lots of things are open to interpretation, which is why writing about history isn't a science. The way you put together "unique documents" will change the interpretation of history.