My preference, for the US, has always been DeLorme's Street Atlas. It isn't free, but it usually has excellent maps down to the places where the dog crossed the street to chase the cat. For another few bucks you can get a package with a GPS Satelite receiver included as well, to tell you where you are on the map on the screen.

Although the program will print out great maps, an even more useful feature is to take a screen shot of the portion of the map that interests you, copy it to a grpahics program, and reverse it. Printing this, as is, gives you a mirror image of the map that can be placed on top of your instrument panel and read, right side up, off the inside surface of the windshield! A low tech version of a heads up display that doesn't require you to take you eyes off the road ahead to read the map.

I'm sure DeLorme doesn't recomend this tip!

Dave