The new Acura NSX hybrid concept car
From this Wired article by Matt Hardigree
Check your car's gas mileage
Government site for researching gas mileage.
If you fall below a certain level, I think 10 MPG, you can qualify for the “Cash For Clunkers” program that will give you a voucher for $3,000-4,500 for a new car. Chrysler has a deal where they match the voucher too.
Still not as cost-efficient as buying used, but still a deal for a new car.