Green car mod roundup Answered
Treehugger has a nice roundup of mods that people have made to their cars to make them more efficient or run on alternative fuels. They even included the Honda Accord that runs on trash in the list, which is pretty cool. Other mods include wood-burning cars, biodiesels, wood-burners, solar-power, hydrogen, and aerodynamic enhancements. Check out the link for the slideshow.
Note: there are 17 slides, not 17 cars.
17 DIY Cars Hacked for Fuel Efficiency