Unless you live in a VERY rural area, AND follow the keep right laws, please don't do this.
Hypermiling is when you drive like a 95 year old legally blind person in order to wring out some additional fuel economy from your 2004 Prius, although you can be a douchebag in pretty much any car. In addition, the driving habits and common modifications to one's car are usually illegal.
Now that Gaddafi has found solace in bombing his nation's own oil-wells, among other middle east news, crude prices are predictably rising accordingly. This means that "news" outlets such as Good Morning America (known for such compelling journalism as this and this) are doing another round of Hypermiling and "how to increase fuel economy stories". Noticeably missing from all of these is "stop buying stupid cars that get horrible fuel economy in the first place", but I digress.
Here's the problem with hypermiling in an area where others actually drive. YOU CAUSE TRAFFIC JAMS. Ironically, while you might save 15% more fuel, you just increased the consumption of the 20 cars you prevented from making the light behind you by 5-10%*. Now I'm not a mathematician here but... This is just an active way of driving too slow for the circumstances and road conditions. I'm all for efficiency, and on paper its really not a terrible idea - smooth throttle, avoid braking unnecessarily, shut off if idling for an extended period of time - but in the real world it usually doesnt work. I'm not saying use the brake/gas pedals as digital switches, and some techniques should be employed anyway. I'm saying don't actively do this in an urban (hell, even suburban) area where you'll cause problems with anything from safety to traffic flow. Also, does all the money you're saving by switching of the motor if idling for more than 10 seconds go into a fund to buy a new starter too? The increased wear on the car alone makes constant on/off cycles not worth it in the long run.
*numbers made up, like 84% of all statistics