Temporary electric four wheel drive for cars. It would only be to get you going in difficult conditions, eg snow, mud. The basic idea would be to have electric motors on the normally free spinning wheels, they would only need to work at low speed just to get the car moving. [July 2011]
Multiple armatures on hard disks. To improve at least read performance, perhaps write if the logic could be figured out. So one spindle, multiple arms (not just heads/platters). This is probably something that was done in the early days of computing.
And again, the new Volvo XC90, will have the front wheels driven by conventional engine, and rear wheels by electric motor.