Images: 100 miles per gallon or bust!

Car makers are already charging batteries, tuning engines, and inflating tires to get ready for DARPA's Progressive Automotive X Prize contest, which will deliver $10 million to the winner whose car can exceed 100 miles per gallon. At the New York auto show last week, the Defense Advanced Research Projects Agency unveiled Progressive Casualty Insurance as the sponsor of one of the most interesting auto contests to date.

We'll take our second look at some of the competitors. (The first batch is here.) The cars in this gallery were chosen to show off some of the more interesting concepts and designs. Contestants range from small garage owners to companies like Tesla looking to find a niche in the luxury car business.

FuelVapor Technologies of British Columbia developed a three-wheel car called the Alé (left). It contains an engine that runs off gasoline fumes instead of the gasoline itself. The company estimates that a 10-gallon tank full of gas can run for 15 hours. Plus, it goes from 0 to 60 mph in 5 seconds. The Alé was featured on NBC's Today Show and at the New York auto show last week.