I just love Google Earth, and use it as a reference for model design (I design architectural cardstock models). Google Earth has (at least) two features that really make it stand out.
Resolution - for major cities, the resolution is sometimes amazing. In Manhattan you can clearly see individual pedestrians. It's not yet high enough to make out models of cars, but you can easily make out different types of vehicles. I believe these highest resolution shots are taken by aircraft, not satellite.
"Tilt-o-matic" (or whatever Google calls it) - if you install the app, you can adjust the "tilt angle" of the images. When you line up the angle of tilt correctly with the photo's original perspective, magic happens. Unfortunately, the photos don't have a consistant perspective, so you have to occasionally adjust the angle, but ... wow! A flick of the mouse, and you are drifting along with a view just like you would have from a balloon. Simultaneously play an mp3 of wind sounds or urban noises, great fun, especially if you happen to be a homesick American living abroad.
Natural features also look surprisingly three-dimensional when tilted just right. It's fun to "drift" along over the Rockies, check out Mt. Saint Helens or craggy glaciers in Greenland.
I was amazed to see high-resolution coverage of Shanghai (China). I can see my apartment building here in surprising detail.
I mentioned Google Streetview earlier. If you haven't heard of it, it's the same idea, only instead of a point of view from above, the POV is from street level. They drive around cities (only a few so far) in cars equipped with camera-filled domes. The resulting images are "stitched" together, so you can "walk" down a boulevard with a photographic view of the buildings that line it. I had great fun "visiting" former residences and haunts in San Francisco. The resolution of the images is not that high, but as a harbinger of things to come ... oh!
Google Earth, Streetview, SketchUp - such terrific free products, so very nicely designed. Too bad the company is so sketchy.
