FixedContent.js is a mobile-friendly jQuery plugin that fixes/sticks content while scrolling.
A.K.A. sticky sidebar, persistent nav, fixed menu, etc.
There are also some settings builtin that you can customize, like e.g. a fixed margin-top (margin will remain as the page is scrolled), a min-width value (disables the plugin on mobile devices or narrow screens) and a z-index value.