So I finally got my hybrid Toyota Prius, 6 months after ordering it. (I put on the "Al Qaeda Hates This Car" bumper sticker soon afterwards.) The car has a video display that shows when it's using the electric motor running off the battery, when it's using the gas engine, or both, and shows the gas mileage you're getting at that particular instant. So if you drive it just right, accelerating and decelarating sloooowly, you can just use battery power and hit the 99.9 miles per gallon.
The result is a much more meditative, slowing of acceleration and decelaration - as long as there's noone following you that's going nuts. I kind of like it, and wish I could've tried it sooner.