GA Scroll Reach
Track how far your visitors scroll down a page in Google Analytics with this jQuery script.
To install, simply place this script beneath your jQuery script and your Google Analytics script. Obviously you will need jQuery, but you'll also need Google Analytic's Asynchronous script ready.
This script is WTFPL licensed except for the cookie functions from Quirksmode.
For more information about this script, please visit: http://www.optimisationbeacon.com/