Here's a site that has exactly what I want. I was unable to isolate just that part of the script from their code. But as you can see on the left side menu, it will smoothly move down the page as you scroll, then before it reaches the footer, it no longer scrolls down with you.
[url removed, login to view]
I prefer that this code used the following div id's: id="footer" and the fixed menu div id="article-contents".