Stampit
Create objects from reusable, composable behaviors.
Jquery Timeago
Timeago is a jQuery plugin that makes it easy to support automatically updating fuzzy timestamps (e.g. "4 minutes ago").
Page.js
Micro client-side router inspired by the Express router (~1200 bytes)
Chaplin
An Application Architecture Using Backbone.js
Postal.js
JavaScript pub/sub library supporting some advanced subscription features, plus message capture and replay
Csso
CSS-optimizer
Flux
Application Architecture for Building User Interfaces
Foundation
The most advanced responsive front-end framework in the world. Quickly create prototypes and production code for sites and apps that work on any kind of device.
Node Decorators
node-decorators
Layzr.js
A small, fast, modern, and dependency-free library for lazy loading.
Montage
Core framework: Montage simplifies the development of rich HTML5 applications by providing modular components, real-time two-way data binding, CommonJS dependency management, and many more conveniences. Join us on irc.freenode.net#montage or https://groups.google.com/d/forum/montagejs
Framework7
Full Featured HTML Framework For Building iOS & Android Apps
Alertify.js
JavaScript Alert/Notification System
Qooxdoo
A Universal JavaScript Framework
Node Browserify
browser-side require() the node.js way
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.
Winjs
WinJS project by Microsoft Open Technologies