3difier is a project mainly written in JavaScript, it's free.
Generate https://github.com/404 parallax effects dynamically with javascript.
This script allows users to dynamically create a Javascript Parallax image a la https://github.com/404 or https://github.com/500.
Each object requires a x and y coordinate, a depth corresponding to how far "into" the image the object is and the url of an image. Optional parameters include width and height and invert_x and invert_y.
All of these methods can be chained, ie: $('#test').threedeeify('init',{"width": "900", "height": "400"}).threedeeify('add_object', objects).threedeeify('start').threedeeify('debug');