GEFS is a game in which you fly a plane (but you have a big variety) and you can play multiplayer by logging in with Google (and without logging in, too). In my opinion I think it is the best online simulation game. This is what you need:
- Google Earth plugin
- a little simulation experience
- and enter: http://www.gefs-online.com/
The game is made by a single developer and he’s not a Google worker.