I really love the idea of the library success wiki, I stumbled upon it a while ago but hadn't gone back but I'm impressed by how much it has grown: I guess all us library folk doing the 2.0 training has encouraged more contributors!
As for wiki use in a library setting I think the possibilities are endless. My library has a wiki called the Library Ideas Bubble where we put ideas up which other staff can then flesh out or to wait until the right time/funding becomes available etc. It's a way that we capture our ideas.
The South East Local Studies Network that I am apart of also has a wiki for us to post questions, put up things we're working on, meeting minutes etc. It works particularly well as the SELSN comprises of libraries that are hours and hours away from one another.