You have probably already seen over a hundred uses for Google Maps. Today, I received a link of a new use: Goggles. Goggles allows you to fly a plane over a city, to climb and descent, to shoot at the scenery (I tried this over Amsterdam but didn't hear anything on the news. It's safe!). You even can crash.
A while ago I thought on developing a game on Google Maps too. No action-game, no flight simulator, but more a strategic game. Imagine a sort of Risk or Transport Tycoon on satellite imagery. Unfortunately, I didn't find the time to even think about a nice game concept. Maybe once!