Parallax scrolling sites have been a pretty hot UX thing of late, being showcased on various blogs. Although the “ooooh! aahhh!”-ness of it all has subsided, I think this type of site is certainly a legitimate design and development option for many brands.
To help you choose a JavaScript or jQuery library or plugin for doing this sort of thing (unless you’re a masochist and want to write one from scratch!), in this post I’ve put together a list of plugins and scripts to choose from.