Dating back to 2001, Penn Robotics (Team 135) used a dual-wheel per axle, crab-style drive system. It was extremely fast, and very maneuverable. Those kids obviously had some stick time behind it, as it was a blast to watch.
Here's a pic I dug up from the 2001 KSC regional. Maybe someone from the team can tell us a little more about it?
FRC135, 2001