Google's beta maps is an excellent, free mapping source (maps.google.com). Now they've come out with a free satellite imaging service at earth.google.com, where you can zoom in and out of satellite images of apparently most of the earth. I looked at a satellite image of my apartment building in Manhattan!

While I haven't tried it, they have a $20 service which, it says, ties into GPS and has drawing tools. One day, this might be useful for creating bike routes and maps.