Even the world’s fastest cars are getting it. Whether it’s for love of the planet or money saved at the gas pump, the desire for fuel-efficient cars has reached the tipping point.

Back in 2000, the Prius Pioneers bought the first Toyota hybrids online, sight unseen. By 2005, Toyota had sold 100,000 of these uniquely shaped cars. Honda was in second place with Insight and Accord. Ford was blazing trails, if not sales, with the first hybrid SUV. Then Katrina hit.

In a matter of weeks, fuel efficiency topped the charts for new car buyers with 30 percent saying they would ‘strongly’ consider a hybrid. By the Frankfurt auto show in October, hybrid fever was in full swing. With Toyota and Honda hybrids achieving record sales in the North American car market, the big automakers were feeling the heat. With a lot of fanfare, GM, Ford, BMW and even Porsche announced they would be greening their fleets.

So what are the most fuel-efficient cars on the road today? Corporate Knights and Zerofootprint joined forces to find out. We’ve rated over 1,000 cars in seven categories in the mid to lower price range. But if the green stuff is no object, you can order a custom, fuel-efficient and very fast car like the one on the cover for $140,000 U.S. from L3Research in California. For the rest of us, here are the top seven fuel-efficient vehicles in our first of a series of green buying guides.