Fill it up, plug it in, then drive. And drive. And drive.
That's the dream, anyway, of an Idaho National Laboratory http://www.inl.gov program testing 13 Toyota Prius hybrid cars retrofitted with mileage-boosting batteries that can be plugged into a regular household electrical outlet when they're not in use to give them more oomph on the roads.
Full Story: http://www.idahostatesman.com/business/story/203900.html