How does Yahoo do this? If you scroll down this page you'll notice that the right rail content will stay visible until you get to the bottom of the article. My guess is it is a combination of jquery/css. Are there any examples out there on how to do this.
In general, this technique is called 'Follow Sidebar'.
This tutorial is exactly what you see on Yahoo link you had posted: http://techbrij.com/fixed-sidebar-scrolling-jquery-div
Other than that, there is an example of a 'simple scrolling sidebar' here: http://css-tricks.com/examples/ScrollingSidebar/