Now, when you say "discuss projects and ask questions" are you thinking wiki interface for discussions, maybe a sort of GetSatisfaction type idea for discussions, maybe with voting?
Even Github lacks some neat discussion systems that might be nice to see somewhere.
Provide a realtime chat if you can, ie like:
https://github.com/isaacsu/twich
Give it a timetable so each project has a set time for participants to chat, (the project in question is displayed at the top of a page.) You can also record chats, and offer multiple rooms.
Even Github lacks some neat discussion systems that might be nice to see somewhere.