Mac: Sometimes, you just don't want to touch a keyboard or mouse. ControlAir is an app that allows you to just raise a finger in view of your Mac's webcam to control your media.
ControlAir works with iTunes, Spotify, Rdio, Netflix, Quicktime, VLC and Vox. To use it, simply raise your finger, then move it left or right to select the volume buttons, play/pause buttons, or previous/next buttons. When you're on the one you want, "air click" to select. It's a little silly, but still fun to check out and use for a little while. It works surprisingly well, as long as you're within about 1.5 metres of your camera.