Zoom.js
zoom in on any element in the DOM
Phantomjs
Scriptable Headless WebKit
Scrob Master
Master your scroll events.
Zepto
Zepto.js is a minimalist JavaScript library for modern browsers, with a jQuery-compatible API
Vissense
A utility library for observing visibility changes of DOM elements.
Veinjs
Injects CSS into the document (it's a perfectly legal procedure)
Atom
Atom javascript framewok
Porthole
A proxy to safely communicate to cross-domain iframes in javascript
Fastdom
Eliminates layout thrashing by batching DOM read/write operations
Masonry
Layout elements in a grid, like a mason fitting stones in a wall
Do Mtastic
Small & fast DOM and event library for modern browsers.
Bespoke.js
DIY Presentation Micro-Framework
jQuery Evergreen
Small & fast DOM and event library for modern browsers.
Handorgel
Accessible W3C conform accordion written in ES6.
Viewport
Gets the dimensions of the Viewport and beyond.
Elements
E+lements is a minimal DOM Library for the prime framework.
Wow
Reveal CSS animation as you scroll down a page