Up for a good challenge and have a lot of free time on your hands? Then you might want to start learning how to build an engine. The X-Prize Foundation, the organization that gave $10 million to SpaceShipOne two years ago for achieving the first civilian space flights, is offering a new contest: build the world's most fuel-efficient car.

The contest, reported in the Christian Science Monitor, will be announced later this year. It's unclear how big the prize pot will be. But chances are good the competition will send entrepreneurs and innovators scuttling to create a super-efficient car that can be made on the assembly line.

The foundation's chairman, Peter Diamandis, told the Monitor, "We believe the time is ripe for a fundamental change in what we drive - and we believe an X-Prize in this area can drive a substantial change."

The Monitor also reported that other potentially lucrative oil-related competitions are in the pipeline, including the absurdly titled "Freedom Prize": a kitty from the DOE for "tangible methods to cut US dependence on imported oil," which seems like it could mean anything from alternative energy to drilling in the national parks.

Photo credit: hybridcars.com