There is this fun and simple flight simulator running on Google Maps. The game is named Goggles Flight Sim v0.94. It uses Google Maps API and a cute little animated plane. You can fly up, down, left and right to control the plane's direction. In addition, you can shoot little pellets into the air. Finally, if you keep going down, you will crash and explode, so be careful.
Forum discussion at Search Engine Roundtable Forums.