Parallax.js is a robust little parallax engine, giving you a quick, simple api to get going with all your parallax needs. Forget scrolling though, parallax.js utilizes your devices orientation and will fall back to cursor positions if no motion detection is available… this really gives you that sexy responsive feel.
Apart from being open source, the project also has a beautifully designed demo page, really showing off the libraries full potential (be sure to check it out on mobile, or iPad!)
Parallax.js by Matt Wagerfield (@mwagerfield) and Claudio Guglieri (@claudioguglieri)