The Arctic Cooling Twin Turbo cooler worked surprisingly well for my GTX 480. Much quieter than the reference cooler and kept it much cooler at load. I got it on sale for $30 a while back.
I ended up de-lidding my GTX 480, and that made an even bigger difference in temps. I believe with a 20% OC and a slight voltage bump, it would not break 80C after 10 mins of the heaviest possible load i could throw on it with Furmark. Not bad!