www.philly.com/inquirer/opinion/20070404_hidden_cost_of_driving_a_Prius.html
In short, the nickel for the battery has to be mined in northern Ontario, smelted (inside a sulfur dioxide spewing plant), shipped to Wales for refining, then to China, where it's made into Nickel foam, and then to Japan.
Not very clean, but really, the car is all about image, not efficiency. That's why I call it the Toyota Pious.
Thanks!