BuddyPress.org

There are a couple of solutions.

One is to just use the bp group forums as is. mikepratt has a nice example of this at http://buglenotes.com.

johnjamesjacoby has the bbGroups plugin working over at http://delsolownersclub.com/discussions

fishbowl81 has taken a different approach with http://gorgeousgamers.com/beta/forums/ with the discussion starting about this in https://buddypress.org/forums/topic.php?id=1321