Here's an informative article about a competitive hypermiler.
The guy is using some dangerous techniques. I have to believe that Rush Limbaugh would lampoon the poor guy, but the basic concepts are certainly applicable to anyone driving anything. Most people aren't going to drive with the windows rolled up, the AC off, and no fan, much less take a 25 MPH curve at 50 MPH, but it's really simple to stretch the tank for a few more miles. Tired of dropping all that money at the gas station? Getting good gas mileage isn't only dependent on the car: it's mostly dependent on the driver.