I have been hearing a lot of good things about the Dash. It's based on open source and is internet connected. It recognizes other dash users on the road and based on their speed vs the speed limit of the road, it will give you real time traffic volumes. You also get real time speed trap reporting, yahoo local etc.
You can even get the price of gas at various stations around you and find specfic things near you or your destination.
http://www.dash.net/