Servos are among the most useful components in the inventor's arsenal. I know that whenever I need to make something move on it's own, a servo is usually the first thing I reach for. A couple years ago, CCCKC member Craig Berschiedt taught me how to turn a normal RC project servo into a continuous rotation servo. The trick involves modifying the mechanics of the axel to rotate a full 360 degrees, but also to modify the electronics to allow for controlling speed and direction of rotation rather than position.