Until Kinect and Tobii get miniaturized enough to fit into a laptop that won't crush your femurs into calcium supplements, a startup called Flutter offers a simple way to control music and movie playback with hand gestures using even a webcam as terrible as the one in a netbook.
Flutter's secret seems to be that it's not trying to do anything fancy. There's no infrared illuminators, no stereo vision, and no 3D depth perception. All the software does, really, is to use your webcam to look for your open palm, and when it sees that, it'll either pause or play your media. It doesn't require calibration and will work in anything short of complete darkness. Simple.
Behind the scenes, Flutter has algorithms working hard to tell when there's a palm in front of your camera and not some other body part. Currently, this only works with iTunes or Spotify (and only on Macs), but the people behind the software are looking to diversify a bit, offering more gestures on more platforms (like Netflix and YouTube) without sacrificing the lack of complexity that makes Flutter appealing to begin with.
Flutter is in alpha right now, but you can try it out for free at the website below, after checking out a video (also below) showing how it works.