Originally designed in Switzerland, this 2 seater combines Muscle Power (yours) with an Electric Engine. 
According to the Twike US site the vehicle retails for around (ouch!) $27500 and you have to get on the waiting list for 2008 models to get one.
Illustrating the Pedal don’t Pollute adage.
Have you driven a Twike lately?
Also on Green Taxis and More: The Green Buzz is On…Yahoo offers 2 Earth friendly sites