https://github.com/justMoritz/sapopin.js
SA (Scrollimate) Pop-In is a simple and easy jQuery based Plug-In that allows elements in your document to “pop in” when they are scrolled into view. Either from the bottom (default), the left or the right.
When the page is scrolled back to the very top, and then scrolled back down, the elements will pop into view again.
SA Pop-In is featured on schrift.co.