If Google Maps wasn’t good enough to begin with, they had to go and add satellite imagery from their Keyhole acquisition. After navigating around on Google Maps to find a location of interest, click on the Satellite link in the top right corner of the screen to switch to satellite image mode. If you’re looking for obvious landmarks, though, sometimes it can be faster to navigate in satellite image mode.
While similar features have been available from websites like TerraServer for many years, Google does a great job of packaging things in a convenient, easy to use interface. I don’t doubt that there is a lot of wizardry under the covers, but the clever UI still comes off as the most astonishing aspect of it all.