Group/Team Communication

I am working on a WordPress website for a newly formed non-profit organization. They are seeking methods for easy communication and exchange of ideas, tracking problems, etc. The easy route would be to use email. Probably the best option I know of is to create a private forum for only group members.

My question is, are there other methods for this type of collaborative effort? From what little I have seen at this point, something like Google Wave may be what I’m asking for, but I was curious if there were other options in the interim until Wave is available.