Meredith has put together a wiki for ALA Annual. Its content includes not what is happening within the conference itself (although that would be very helpful), but information about visiting Chicago (restaurants, hotels, attractions, etc). This is very cool and will hopefully be added to by many of the conference attendees.
from Library Stuff
I think conference wikis will become very common.
One wonders if it would almost be worth forking off a custom wiki with built-in features to support conferences.