vail
park city
mamoth/june
keystone
breck
i mean, it all depends on what you really want to work on...if you really want to improve your rail skills, head to keystone. The jumps at Breck are really nice. Mammoth/June/vail are all really nice "all around" resorts (rails=jumps), oh and park city has some really cool rail features, aswell as some pretty nice jumps