Ember.js : A JavaScript framework for creating ambitious web applications
Prototype : Easy Ajax and DOM manipulation for dynamic web applications
loglevel : Minimal lightweight logging for JavaScript, adding reliable log level methods to wrap any available console.log methods
InstantClick : InstantClick is a JavaScript library that dramatically speeds up your website, making navigation effectively instant in most cases.
TogetherJS : TogetherJS is a free, open source JavaScript library by Mozilla that adds collaboration features and tools to your website. By adding TogetherJS to yo...
Modest Maps is a small, extensible, and free library for designers and developers who want to use interactive maps in their own projects.