http://www.waze.com/
Seems like you need lots of people to make this thing work well. But the concept is great. Compiles data from drivers and figures out where the traffic is the least.
Meet Waze - a fun, community-based GPS traffic and navigation app.
Join forces with drivers in your area, easily report what's happening on the road and get turn-by-turn navigation that automatically re-routes you when road conditions change.
That way everybody's commute gets faster and safer. Smart, right?