The effect i am refering to is visible at http://whyinteractive.com/showreel. The elements appear to scroll behind and in front of one another at different speeds creating some cool effects. How was this done?
What you are looking for is called the Parallax effect.
You can learn more at sites like:
http://stephenmcintyre.net/blog/jquery-parallax-scrolling/
UPDATE:
This is pretty much exactly what you need:
CODE: Build a parallax scrolling website interface with jQuery & CSS
DEMO: Parallax Scrolling