I came across an interesting puzzle on the Humanized site through one of my feeds. The puzzle was to design a car that is not forward/reverse modal (basically do away with the gear shift, which creates multiple modes for the accelerator). There were quite a few interesting and innovative solutions, with suggestions ranging from using joysticks to providing separate buttons/pedals for the reverse functionality.
While going through this puzzle and the answers, I came across the Airtrax site, which designs omni-directional vehicles, i.e., vehicles which can move in any direction. They have a small video on the front page demonstrating the vehicle capabilities, and also a page with some information on the omni-directional drive system.