Best mountain within the US, not counting AK, is Jackson Hole WY. Sick terrain in and out of bounds. Actually taking a week trip there soon to explore the backcountry with my buddy who lives out there. Whiteface in Lake Placid, NY is sick as well. Statton, Killington in VT. Around here there is not much, but within a few hours I would say my favorite is Seven Springs, PA. The mountain is divided up nicely with a front and back face, so the crowds don't seem to be as thick as say Whitetail, Roundtop... Just my 2 cents.
For anyone who is interested in snowboarding, especially watching sick snowboarding videos, if you haven't checked out "That's It, That's All" yet, your missing out. The people making the film spent a good deal of money, around 2 million I think, to make this video. It has some of the best cinematography I have ever seen in a film like this (Surf, snowboard, etc.) Travis Rice's section is insane, and most of it is shot in Jackson. Here's the teaser. http://www.youtube.com/watch?v=LoF6TS4lSGk
in the country I like Bridger in Montana. It's small compared to neighboring Big Sky but doesnt have the crowds and has better tree runs. Plus, it's where I learned to snowboard when my aunt and uncle used to work there.
Around here I like Roundtop...the drop on Upper Gun Barrel being the sole reason why. It's one of the few natural terrain features in this area that I feel is actually challenging. It's kind of fickle though cause a lot of times there either isn't enough snow or it develops huge ice bumps and 5 foot ruts carved into from everyone taking the same line.