I have been thinking about self-driving cars quite a bit lately. Wired Magazine has a great article in the current print issue about the different technologies that automakers are employing to make the autonomous car a reality. They also posted a great gallery of autonomous cars through the ages.
Koushik Dutta wrote a very interesting post in his Google + about how autonomous cars might create a situation where we no longer own cars as individuals but rather share them, since most automobile are parked 96% of the time, doing nothing.
Finally, I built a project in Scratch to simulate an intelligent car that can sense whether it might be on a collision course with an obstacle.
The vehicle has a distance sensor built into the front. Scratch reads the distance sensor values and adjusts the motor speed accordingly.