We've been using TWiki now for about a year to support our courses, and it's been incredibly successful. I've been meaning to write someting up about it, but just haven't found/made the time. Interested parties can check out
A short"Why wiki?" outline for a presentation I gave to some faculty and staff about our experience. Most of this is old hat to the TWiki community, but the discussion of usage statistics and the value of a dynamic (=alive) vs. static (=dead) pages may be of interest.