This probably takes the cake as far as DIY projects are concerned. Any self respecting car loving geek should give it a go. After all its not everyday that you get an opportunity to make your own hybrid.
The XR3 Hybrid is a super-fuel-efficient two-passenger plug-in hybrid that achieves 125 mpg on diesel power alone, 225 mpg on combined diesel and electric power, and performance like a conventional automobile. At just 1480 pounds, this high-performance design combines fast acceleration, a maximum speed of 80 mph, and fuel economy of 125- to over 200-mpg.
The XR-3 Standard Plans Package is $170. The package includes eighteen D-size (24 x 36 inch) drawing sheets, one 32 x 64 inch full-size template sheet, and a 149-page construction/technical manual with over 200 photos and illustrations. The XR-3 Deluxe Plans Package is $200. The Deluxe version includes everything from the Standard version plus two CD-ROMs and one DVD.
Creating the car itself would cost anything from 10,000$ to 25,000$ USD.
Get the full details at the official web site.