Here's another piece of gungasnake advice: don't buy any of the hybrids. They're going to make horrible used cars and it's basically just the Japanese who are sold on them, the Germans don't want any part of the idea and are mainly moving towards diesals, at least for now.
Aside from new engines and new fuels, future cars are going to use new materials, mainly carbonfibre, and be a lot lighter, and that translates into very noticable fuel savings as well as general savings on wear and tear, a lighter vehicle simply is not under as much stress. There has been a steady upwards creep in weight for small cars over several decades. Typical small cars in 1968 or thereabouts often weighed under 2000 lbs and did not need or have power steering. Those days are going to come back.
Aside from diesals, there is a strong possibility of all electric cars with enough range to be totally useful, hydrogen-fueled cars, and several other possibilities. One idea which strikes me as interesting is this:
http://www.angellabsllc.com/