jQuery keepInWindow ist a jQuery plugin which allows you to keep some elements always in the viewport.
Usage is as simple as: $(".elements").keepinwindow();
If the cursor is over the element and the element has a greater height than the window it won't move.
See the examples folder for examples ;)
Demo: http://sopamo.github.com/jQuery-KeepInWindow/
Download: https://github.com/Sopamo/jQuery-KeepInWindow/zipball/master
Blog entry: http://4ppletree.me/jquery-plugins/jquery-keepinwindow/ (german)