Hydrogen, of course, is still a popular green source. The Volkswagen Space Up! is one example. it is a rear wheel drive mini-minivan that seats four and is powered by a hydrogen fuel cell and electric motor. Course automakers -- and law makers for that matter -- don't go into a whole lot of discussion as to when hydrogen pumping stations will be available.
Besides fuel, automakers are now looking at car design to maximize fuel efficiency. Concept cars are showing a marked trend towards smaller, lighter cars, that are more efficient. Designers are also disregarding the once dominant, and separate, categories like sedans, vans, etc. One just has to look at the Mercedes-Benz R-class to see the lines between vehicles blurring into the sheetmetal.
Finally, automakers are simply putting a stop to certain "gas hogs". Ford put a chill on the latest F-Series, for example. Word on the street now is that a 4-cylinder is in the works.