jQuery Textcomplete
Introduce autocompleting power to textareas, like GitHub comment forms have.
Buster
A powerful suite of automated test tools for JavaScript.
Red Script
A Ruby Flavored Language
Sound Manager 2
A JavaScript Sound API supporting MP3, MPEG4 and HTML5 audio + (experimental) RTMP, providing reliable cross-browser/platform audio control in as little as 10 KB. BSD licensed.
JSON.js
JSON in JavaScript
Keymaster
A simple micro-library for defining and dispatching keyboard shortcuts. It has no dependencies.
Hitch
A lightweight engine that allows you to hitch new capabilities to the browser (prollyfill).
Dimple
An object-oriented API for business analytics
Fotorama
A simple, stunning, powerful jQuery gallery. Licensed under the MIT.
Phaser
Phaser is a light-weight 2D game framework for making HTML5 games for desktop and mobile browsers
Canvas Engine
Framework for HTML5 Canvas oriented 2D video games
Sprintf.js
sprintf.js is a complete open source JavaScript sprintf implementation.
Favico.js
Make a use of your favicon with badges, images or videos
Idle.js
Javascript activity library for the browser. (away, idle, etc)
Double
jQuery plugin for hiring doubles
Annyang
A javascript library for adding voice commands to your site, using speech recognition.
Babylon.js
Babylon.js: a complete JavaScript framework for building 3D games with HTML 5 and WebGL