The EPA released its fuel-economy report for the 2006 model year, and hybrid or diesel engines power 9 of the 10 most fuel-efficient cars. It's not too much of a surprise, since hybrids are designed to capture wasted energy and put it back into the car, making an obvious improvement upon gasoline equivalents. Diesels have long been known for greater fuel efficiency over gasoline. Readers of CNET Car Tech occasionally ask why there isn't a diesel hybrid to get the best of both worlds. I've heard that Audi worked on the idea some years ago, and I can only speculate why there aren't diesel hybrids right now. It's possible that diesels are so efficient that any increase offered by hybridization is too small to justify adding the hybrid system.
I was pleased to see that the Ford Escape hybrid made the top 10 list of fuel-efficient cars. The only straight-gasoline car to make it on the list was the Toyota Corolla. You have to give Toyota credit for some fine engineering. On a related note, Ford dropped the Excursion from its lineup, which wouldn't have been anywhere near the top 10.