Scrolling Parallax jQuery Plugin
The Scrolling Parallax Plugin binds a jQuery event to the scrollbars and mousewheel, which causes the background image to scroll at a different pace from the web page.
Scroll down to see Scrolling Parallax in action
Easy To Use and Extensible
The Scrolling Parallax is super easy to use, you can either pass it a path to an image or call it on an existing piece of HTML markup by using a jQuery selector.
It also has a wide variety of options, with controls for scroll speed, scroll direction, looping the animation, tiling the background and manipulating dimensions.