Natural gas: Natural gas as an alternative fuel has some excellent advantages. First it is very environmentally friendly. Cars running off CNG produce less smog pollutants and less greenhouse gasses. Also, natural gas can be less expensive than gasoline.

Hydrogen: Hydrogen may the alternative fuel of the future. It's a bit less developed than some of the other fuels, but it has some great potential. Hydrogen is often used to power fuel cells for electric cars, but it can also be used to power internal combustion engines.

Hydrogen has the great advantage of producing little to no pollutants or greenhouse gasses. What a deal! It can also be produced locally, easing the reliance on gasoline and oil.

Alternative fuel sources