If you're looking for a highway cruiser, a G1 Insight can't be beat. Rather, other than the limited production VW XL1, which is $150,000, no other stock car on the road will beat it. The original EPA highway figure was 70mpg.
You can get a clean and problem-free Insight for $3-4500, and they are extraordinarily reliable. IMO, the seats aren't very comfortable, but some people like them a lot.
EDIT: Check out my modding thread:
http://ecomodder.com/forum/showthrea...tlc-29288.html