Now this would honestly have to be one of the coolest things I've ever seen, but yet to personally use myself, unfortunately. NVIDIA have teamed up with Keyhole to you give us a program called EarthViewer 3D, an amazing program which lets you zoom around the world using satellites delivering a constant streaming 3D representation of the entire globe. There is a catch though, you need at least a NVIDIA GeForce2 to use the program, other users of different video cards from other manufactures will be at a loss.
Keyhole fuses high-resolution satellite and aerial imagery, elevation data, GPS coordinates, and overlay information about cities and businesses to deliver a streaming, 3D map of the entire globe.EntCity.com wrote up a little bit of a preview, check that out here. I'm impressed!
The result is a whole new way of looking at your world - reach out and "grab" the earth with your mouse, pan quickly to your area of interest (or select it from a placemark) and then zoom smoothly down to an individual building. Watch as the city unfolds itself before your eyes, revealing new perspectives and fresh insights.