This looks like a handy tool for implementing a sticky nav bar.
Box Tech Blog » Stalker, a JQuery Plugin That Follows Users on a Page
When we designed the new header for the Box Webapp, one of the goals was to make navigating the site easier and more intuitive, which we decided could be achieved by putting search front and center alongside access to the main areas of the application. In order to have those controls readily at hand and for an enhanced user experience, we decided to have the header follow users as they scroll down a page.
(You can see a very simple demo of how the plugin works here.)