It seems to me that there's a pretty big need for something like BuddyPress but for a single site on a Network install. BuddyPress (please correct me if I'm wrong) requires a Network Activation. However, if you're doing a Network site, not every site owner wants to see all the BuddyPress stuff. So, I thought that your suite of plugins (communities, forums, messaging, friends, chat) would be perfect. Not so, the only one that can be activated on a single site by "Activate on individual sites by going to the Plugins page in any Site Admin" is Chat. Mingle used to do this, but Mingle's not compatible with WordPress 3.1 Network install. If you could modify Communities, Forums, Messaging, and Friends to work on single sites instead of requiring Network activation that'd be GREAT.