Canjs
Can do JS, better, faster, easier.
Spine
Lightweight MVC library for building JavaScript applications
Alloy Ui
Alloy is a UI metaframework that provides a consistent and simple API for building web applications across allthree levels of the browser: structure, style and behavior.
Dojo
Dojo saves you time and scales with your development process, using web standards as its platform. It’s the toolkit experienced developers turn to for building high quality desktop and mobile web applications.
Remote Storage
Client-side Javascript library to make apps compatible with a remote storage.
Sammy
Sammy is a tiny javascript framework built on top of jQuery, It's RESTful Evented Javascript.
Postal.js
JavaScript pub/sub library supporting some advanced subscription features, plus message capture and replay
Chaplin
An Application Architecture Using Backbone.js
Enyo
A JavaScript application framework emphasizing modularity and encapsulation
Cerebral
A state controller with its own debugger
Aura
A scalable, event-driven JavaScript architecture for developing widget-based applications. Works with Backbone.js and other frameworks.
Sproutcore
JavaScript Application Framework - JS library only
Nuclear Js
Reactive Flux built with ImmutableJS data structures. Framework agnostic.
Ink
An HTML5/CSS3 framework used at SAPO for fast and efficient website design and prototyping
Durandal
A cross-device, cross-platform client framework written in JavaScript and designed to make building Single Page Applications (SPAs) easy to create and maintain.
Datacamp Light
Convert any blog or website to an interactive learning platform for data science
Bootstrap.native
If you are looking for Bootstrap without jQuery or vanilla Javascript for Bootstrap, this is the place to get started.