Terran isn't any more overpowered than anything else. Everyone is just playing it because it's the campaign race and all the new people are most familiar with it (and by extension, suck with Protoss and Zerg). As for the placement, it's skewed because of so many new players (SC2 sold 1.5 milllion copies in 48 hours). I haven't actually done my qualifiers yet (will this weekend) because I'm waiting for the ladders to stabilize at least a little bit.
As for the clan, don't need anything too fancy. Eventually battle.net will have chat rooms that we'll be able to set up, but at the moment I don't think it even needs a special forum, if all we're looking for is a bunch of people to play with.