No, there isn't really a central site. The closest one I know of is this: http://www.paloalto.com/academic/competitions/. But there are competitions coming up all the time. Search Google and Yahoo, and check with all the local universities by calling up their entrepreneurship centers in their business schools. You mention Idaho--Boise State has an active entrepreneurship center and sends teams to compete in a lot of the competitions I'm involved with (I'm a frequent judge).

Tim