I must admit I'm not a wiki fan. They're only as good as the people who create and edit them. We tried to use the eXtension wiki to work on a community of practice and found it to be very confusing and not at all intuitive. I think it reflected the thought process of whoever started it. It's also hard to get everyone on a team to work in this way. I think they could be a great tool if everyone was on board.
I set up a couple of the new Google Sites - free collaborative websites that are wiki-like in nature. Haven't done much with them yet.