Groups

[Locke]

I think allowing users to create their own groups (with permission from an administrator) is a good idea.
Unless the project has been lain aside until more people join.

[Mitch]

Actually, your idea has already been thought of.
The software I am using is called vBulletin (www.vbulletin.com) and the new version soon to be released will have Social Networking (Facebook) type features.
If you visit the vBulletin community forums, you can see the demo version running. I will be upgrading as soon as it is released.