Clean Energy Fuels (CLNE -5.38%) has been beaten up on the stock market over the past six months and is now bouncing near a 52-week low. But the company's operations continue to improve and as heavy duty trucking fleets grow, and America's Natural Gas Highway is completed, a big opportunity is opening up for investors. A quarterly loss in the third quarter has a lot of investors running for the hills but alternatives to oil are still a long-term winner and there's a lot of momentum for natural gas.