Bootstrap provides an affix navigation menu component which can make a nav-bar sticky while scrolling within a certain section of a page.
At the time of writing this article, this component is known to have cross-browser compatibility issues which are not yet fully fixed in Bootstrap's version 2.1.1 - e.g. flickering and violent movement of the affix menu when it reaches the bottom of its defined scrolling area/limit.
There are two jQuery based alternatives which can be used to provide a similar functionality -
The only drawback in these alternatives is that when used with menus, they do not provide automatic highlighting of the current menu entry (which is in view) on scrolling as seen in Bootstrap's affix plugin.