This was featured in Pop Science magazine last month. Very interesting article on "hyper-milers"- folks who drive to achieve very high MPG numbers.
http://www.motherjones.com/news/feature/2007/01/king_of_the_hypermilers.html

I've applied a few techniques on my daily driving for the last several weeks. For instance, there's a couple of places where I can shut off the engine for a mile or so and coast on my drive to work. Eliminate fast starts, etc... but nothing to really piss off other traffic. :iceslolan
I've increased my average MPG from 25.5 to over 32 during that period.
-Win