Normally, when you come across a celebrity in Aspen -- say, Kevin Costner fashioning a kayak for an In Stylemagazine photo shoot -- it's funny, but not ha-ha funny. For nearly one week out of every year, though, Aspen is the ha-ha-funniest place in the world. The U.S. Comedy Arts Festival is a veritable all-you-can-eat buffet of humor, from standup to sketch comedy to readings; Cheech and Chong, Conan O' Brien, Jim Carrey and Dave Eggers were among those on hand this year. And how about all those hangers-on in fur coats with VIP passes around their necks, talking on headset cell phones? Now, that's funny.