http://en.wikipedia.org/wiki/Fuel_cell
One thing you should be aware of is that fuel cells are NOT energy sources! Therefore they are not replacements for gasoline unless you can find some way to input energy into them, like through solar or nuclear power. This is an extremely common mistake people make - to assume fuel cells can simply replace gasoline as energy sources for the engine. They can, but you need to put the energy into them first. Gasoline comes ready to burn with plenty of stored energy when you find it.