I'd hate to bring this thread up out of the dead, but there's an iPhone app called Plane Radio which is a database of all FCC AM radio stations in the US and it orders them by signal strength. Which is a function of distance and power (watts) The distance is from the VOR that you input on the app... You can also sort the list using Format like Sports, Talk, Music etc....
http://itunes.apple.com/us/app/plane-radio/id526252422?ls=1&mt=8
