The parallax effect has become a popular way to spice up your site design, so it is helpful to be somewhat familiar with it. There are many plugins, scripts and libraries available. If you have time to explore here are just a few examples to explore.

Pixelcog Parallax seems to be a fairly simple version that relies on jQuery. I was able to recreate their demo in WP as a plugin. Check out

WP-Parallax-Page

As this demo states, the scroll effect does not work on mobile devices. Some of the libraries I checked were buggy. Many of the demos load very slowly, likely because they use several very large images in the demo.