Kefir
A Reactive Programming library for JavaScript
Thrill
Runs tests in many browsers.
Optics
Profunctor implementation of Lenses, Prisms, Traversals, Isos, etc.
JS Movieclip
A javascript little framework to animate spritesheet as AS3 movieclip
Svgeezy
Allows for automatic Image fallbacks for browsers that can't handle SVGs
Stapes
a (really) tiny Javascript MVC microframework
Screenlog.js
Bring console.log on the screen
Objgrep
Find strings inside complicated javascript objects
Limejs
HTML5 game framework for web and iOS
Augment.js
Modern JavaScript in your IE
Apricot
A simple Hpricot Clone for nodejs.
Apitizer
API mocking for client JavaScript applications
jQuery.lazy
A lightweight, fast, feature-rich, powerful and highly configurable delayed content, image and background lazy loading plugin for jQuery & Zepto.
jCanvas
A jQuery plugin that makes the HTML5 canvas easy to work with.
Lity
Lightweight responsive lightbox.
Gremlins.js
Monkey testing library for web apps and Node.js
Color
JavaScript color conversion and manipulation library