Have a new HDTV? If you're looking to find the digital TV station strength and coverage for your hi-def TV, there's no better site than TV Fool. You can input your address or if you know it, your latitude and longitude, and get accurate results and guidance for pointing your antenna.
Even better, the site has converted the data into Google Earth KML files. That graphically shows -- in multicolored detail -- what level of signal you will get at your house. TV Fool even takes into account terrain and earth curvature.

How to aim your antenna
Google Earth's Transmitter Coverage Maps
My buddy Michael McG., who turned me on to TV Fool, also found this cool transmitter map site. TV Fool's owner, Andy Lee, posted a thread showing a neat 3D view of over-the-air transmitters shown in Google Earth.

Local coverage in the Pasadena area