Google Maps Watches from Above
Google has a mapping service which allows you to get maps of addresses, driving directions and other information. I have used Mapquest quite a bit and probably still will, but Google's offering is also quite nice. Its very easy to use, and the maps it generates are simple to view. Recently, though, Google has teamed up with Keyhole.com to provide satellite imagery of the location you are searching for. Now, I can't say that the feature is super useful, at least for me, but I'd be lying if I didn't say it was a lot of fun playing with it. Not all locations have corresponding imagery, but most I searched for did. The imagery is also quite smooth in that you can zoom in and out as well as scroll in any direction without having to totally reload the image.
To play around with this, head on over to http://maps.google.com/ Google Maps. To play with the satellite imagery, click on "Satellite" in the nav bar at the top right.