Short of a technological breakthru in automotive power plants and the fuel they use there's not much one can do.
mhdishere got it right when he said:
If you want to lower prices you have to do one of two things, decrease demand or increase supply
unfortunately since oil is a finite resource even if demand is decreased thru conservation supply is still reduced as the oil is depleted.
Which side of the supply/demand equation gets reduced quicker will determine if prices go down or up. Even with conservation if the supply goes down enough prices will still go up.
In addition the US is not the only demander of oil in the world. If we conserve that just leaves more for other countries and net demand may not go down at all.
IMO we've got to eliminate our dependence on oil as a fuel and that will take new technologies. Best bet now is fuel cells that depend on hydrogen but until some one comes up with a cheap way to produce hydrogen that's gonna be a non-starter.
Who knows maybe there'll be a break through in fusion power reactors and we'll all get Mr. Fusion power plants in our cars. HEY! Anything's possible...