This was big on the blogs a few days ago, but anyhow BeenMapped.com seems pretty neat. Basically it lets people mark of interesting things they’ve found on Google Maps so you can browse them.
For example, someone noticed that the Google Map near Boston captured two flying planes and thier shadows on the ocean. Note, you may have to pan the image down and to the right to see the second plane.
If you keep going you can actually see a third plane