There's a great Wiki being run by Bryant Walker-Smith.
It has the full updates on the legal situation across the US.
Driverless Car HQ
I foresee another very useful function for the systems installed on autonomous vehicles. They would make great recorders for accidents and nearby, aggressive, dangerous fools on the road. I think the inputs from the video, ranging systems, etc. should be constantly recorded and analyzed for incidents that warrant a law enforcement official or agency to be notified. The data could be transmitted automatically and instantly. What a great way to catch the remaining "problems" on the road. If a system like this was in place (which I greatly hope for), the blogger who thinks the autonomous cars would move out of his way would suffer quick repercussions in the form of a fine and points on his driving record. He wouldn't be doing that for long. However, I'm already suspecting that the "invasion of privacy" whiners will do everything in their power to stop a system such as this from being put into place (the same ones who don't want cameras at intersections). We need to find a way to actually start enforcing the laws on the roads. We need to all come up with practical solutions like this for our roadways to be safe and usable in the future - with or without autonomous vehicles.
I'm fairly certain that in the not too distant future, we will think back to these times and wonder why people were ever trusted to drive on their own.
Aside from the GPS and street map data inputs, such as used by the Google system, I think what's required before autonomous cars can become reality is also vehicle-to-vehicle and road-to-vehicle comms. These are the ingredients you need to accommodate all of those real-time unknowns.