From CleanMPG.com:
What is Hypermiling?
Hypermiler is a term coined by Wayne Gerdes to describe a driver who strives to exceed their vehicle’s EPA fuel economy rating. In conventional vehicles they can often match the mileage of an average person driving an equivalent hybrid. Hypermilers driving hybrids tend to achieve tremendous mileage, with some even exceeding 100 [...]

From Wikipedia:
* Hypermilers are drivers who exceed the United States Environmental Protection Agency (EPA) estimated fuel efficiency on their vehicles by drastically modifying their driving habits, sometimes even without regard for the safety implications of other drivers or the law. For example, it is illegal in most states to shut off the engine of the [...]

CNN had a cover story on their website today about Hypermiler Wayne Gerdes and his attempts to get the best gas mileage possible out of his car.
Story Highlights

“Hypermilers” are drivers who push the limits of their cars to conserve fuel
Wayne Gerdes gets 50 miles per gallon in Honda using hypermiling techniques
Gerdes: [...]