FluidTunes

FluidTunes is a remarkable application for OS X that lets you control the Cover Flow interface in iTunes with physical gestures in front of a webcam.

FluidTunes includes four gesture controls: two of them let you browse albums to the left and right, and the other two let you start playing the music and stop it.

Although it may seem like the albums are duplicated, they're not; every song in the album is shown separately with the album cover, so that's why you see the same image a bunch of times in a row. FluidTunes performs better when the contrast between your hands and the background is strong.