Keyhole

Google recently came out with an addition to their empire called Keyhole. Much like Google Satellite, it allows you to view real satellite imagery of just about anywhere you can imagine. Simply type in an address or location, and Keyhole will zoom directly over that area with real imagery (albeit not real-time). Although this service does require an annual subscription, you can download a free one-week trial. The upside to this service over Google Maps/Satellite is that Keyhole shows roads, 3D terrain changes, altitudes, and much more. It's worth checking out even if it's just to play around.