We've seen solar panels utilize spinach which was used to replace the more expensive silicon components, and if going green is your thing, you might be interested to hear that scientists at the University of Southern California have managed to develop a new type of solar cell made from nanocrystals that are apparently so small, you would be able to fit 250 billion of them onto the head of a pin. Thanks to their size, these nanocrystals can be made into an ink and painted or printed onto clear surfaces, thus allowing solar cells to be printed on materials like plastic that can be bent and shaped to fit just about anywhere.
Ubergizmo, Scientists at USC develop solar cells that can be painted onto plastic surfaces
