The FCC has released a new on-line DTV reception tool determine what DTV stations will likely be received at a particular address after the DTV transition. The tool will provide an educated guestimate by signal strength.
If you click on a station's call sign, you'll find technical data about estimated signal strength in +/- dBm, direction to the tower; and pre- and post-channel numbers. If you look at the map after selecting a station, a tower icon will pop up showing the approximate transmitter location.
The tool uses Google Maps technology, so you can click and drag the location icon to a different location to do a A-B comparison. The results will update automatically.