[mpfefferle]

A wiki would probably work well. A Google Site perhaps?

[davidw]

It might - but I'm curious about what people have actually used successfully and any limitations things they've liked about a particular system. Maybe it's worth it's own post...

[rguzman]

Trac is also good. http://trac.edgewall.org/

[phaedrus]

We recently implemented a wiki for our project and it's been a big help.