Holy crap, the new Google Earth just got the 3-D treatment, and it's pretty mind blowing. Play around with it here.
From Google: The whole world is now in your browser. Fly through landmarks and cities like London, Tokyo and Rome in stunning 3D, then dive in to experience them first hand with Street View. See the world from a new point of view with Voyager, which brings you stories from the BBC, NASA, Sesame Street and more.