Breckenridge - Colorado
Breck is one of my favourite resorts for boarding.
They have a few decent terrain parks with jumps and rails. They also have an 11' halfpipe.
The pistes are well maintained, and there are plenty of spots to have a little off piste fun.
Combine that with a friendly feel to the area, a nice old town with a quiteish apres ski environment, and good links to Vail and Beaver Creek, which are useable on specific lift passes, and I don't really think you will find better anywhere else.
The Ski and Board school is excellent too. I don't regret choosing Breckenridge to learn how to board, and I am looking forward to the next time I go back there.