A while ago, I mentioned TVFool.com It's an absolutely amazing, accurate and technical reception prediction engine that will tell you everything you need to know about the TV channels you'll be able to pick up at a given location. This is really an indispensable took.
After much work, they've released FM Fool. Finally, you can get all the same technical information on FM stations that you can on TV stations. Check it out: FMFool.com