One simple suggestion for leading more visitors to the groups:
Move the "Activity"-tab one step left so that it is next to the "Headlines"-tab and give them a different colour. "Headlines" and "Activity" are in my opinion the two best ways of reading Imodeler, one will (quite obviously) give you the headlines and the other one will summarize recent activity in the forums. I have a nagging suspicion that very few visitors venture beyond "Headlines"...
Regards
Magnus