my fiancee sold her car at Regal several months ago. it went for the asking price on the first auction. i'd recommend them if you want to get rid of some junk that is still driveable.
not sure how good it is for still efficient cars, though. selling privately might be a better idea.
my only advise would be price it correctly. not too high, not too low. Regal takes 15 percent, I believe. Might be less, might be more.
http://www.regalauctions.com/