Ionic
Advanced HTML5 Mobile App Framework. A beautiful front-end framework for developing hybrid mobile apps in HTML5. Best friends with AngularJS.
Interact.js
Drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE8+)
UI Router
The de-facto solution to flexible routing with nested views
Kimbo.js
An ECMAScript 5 only-compatible JavaScript library.
Anijs
Declarative handling library for CSS animations.
Grunt
Grunt: The JavaScript Task Runner
Phantomjs
Scriptable Headless WebKit
Velocity
Accelerated JavaScript animation.
Fastdom
Eliminates layout thrashing by batching DOM read/write operations
Isomer
Simple isometric graphics library for HTML5 canvas
Conditioner
Frizz Free, Environment-aware, JavaScript Modules
Knockout Projections
Knockout.js observable arrays get smarter
Riotjs
The 1kb client side MV* library
Winjs
WinJS project by Microsoft Open Technologies
Blazy
bLazy is a lightweight lazy loading and multi-serving image script. It's written in JavaScript why it doesn't have any dependencies for 3rd party libraries like jQuery. bLazy is working in all modern browser including IE7+.
Ect
Fastest JavaScript template engine with embedded CoffeeScript syntax
Famous
Famo.us is a powerful JavaScript framework designed to build rich, interactive web applications. It is the only framework that provides an open source 3D layout engine fully integrated with a 3D physics-based animation engine that can render to DOM, Canvas, or WebGL. Famo.us is currently in public beta.