I highly advise trying this out. It's really mind boggling in the "Enemy of the State" sort of way.
With my obsessive personality, I could sit and play with this _ALL_DAY_LONG_
"Keyhole's EarthViewer3Dâ¢ harnesses the power of NVIDIA GPUs. Fusing high-resolution satellite and aerial imagery, elevation data, GPS coordinates, and overlay information about cities and businesses, EarthViewer3D delivers a streaming, 3D map of the entire globe to PCs powered with NVIDIA GPUs. "
Personal Product: EarthViewer3D