Here is the documentation for SmoothScroll.js.
Smooth scrolling auto targets all the anchors in a page (href="#section", etc.) to display a smooth scrolling effect upon clicking them. To enable for a page, all you have to do is include the script and call:
new SmoothScroll();
You can pass in options (see Fx) if you want. This tutorial uses SmoothScroll when you click on the anchor links in the top-right page nav or the "top" links next to headers.