I think both a forum (async) and some form of IM (sync) communication are needed, but I think IM should really just be just for developers.
Mailing lists are a great option as far as async comms go, but maybe are a little intimidating for laymen for whatever reason. Other than that, they're well trodden and Google Groups is still pretty solid, although the lack of categories (other than just a ton of different mailing lists, which an option)
Mailing lists are a great option as far as async comms go, but maybe are a little intimidating for laymen for whatever reason. Other than that, they're well trodden and Google Groups is still pretty solid, although the lack of categories (other than just a ton of different mailing lists, which an option)