By Jim Karpen on Sat, 02/28/2009
The IPhone Blog has a how-to telling the steps you need to go through if your iPhone becomes completely non-responsive. It entails powering off your iPhone and then pressing and holding the home button while you connect via USB. They also have a post telling how to force quite applications. It's useful not only for quitting an app that has frozen but also for freeing up resources, since some apps such as MobileMe apparently continue to run in the background.