Ok, so this is so freaking cool:
http://worldwind.arc.nasa.gov/
It's a 180 MB download, but man is it worth it. You get a globe that you can click-n-drag to rotate around, and can zoom in with your mouse wheel (or both-click). As you zoom in, you can tell World Wind to download high resolution satellite and arial imagery, all the way down to 1 meter per pixel for cities in the US.
You'll need a high-speed internet connection, and a recent computer (one purchased in the last couple of years).
I recommend this site to learn more about WorldWind
http://www.worldwindcentral.com/wiki/Main_Page
The "official" site is not very helpful.