The US is BIG and there are a lot of climbing and bouldering areas. Some of the more obvious ones are...
Red Rocks Edit
Indian Creek Edit
Alaska (although its HUGE!) Edit
New York City Edit
An overview of bouldering in New York City can be obtained from Gaz Leah's UKClimbing article. He has also written a guidebook (published by Sharp End Publishing) which might be worth picking up if you're heading there. Online topos can be found at Beta-Buy : NYC Bouldering Guide.
As it covers such a vast area there is no single resource for local areas. Best bet is to look for local weather on TV networks/radio.