I crack my window in the winter while I play, and the house has central air in the summer. My game room is never over 70 ambient. The 360 sits vertically on a ventilated shelf with at least 12"+ clearance on all sides. I've never had additional cooling, but if I did it'd have some sort of dust filter added too. Dust is like warm insulation to electronics. I also try not to play more than 4-5 hours at a time without shutting down and letting things cool off.
It sucks that we have to go to such extremes just to play a game.
My PC gaming rig gets similar treatment.