[Web Technology] List of JavaScript libraries

DOM (manipulation) related

• AccDC
• Dojo Toolkit
• Glow
• jQuery
• midori
• MooTools
• Prototype JavaScript Framework
• YUI Library

GUI-related (Widget libraries)

• Ample SDK
• DHTMLX
• Dojo Widgets
• Ext JS
• iX Framework
• jQuery UI
• Lively Kernel
• qooxdoo
• Script.aculo.us
• SmartClient

Graphical/Visualization (Canvas or SVG related)

• D3.js
• JavaScript InfoVis Toolkit
• Kinetic.js
• Processing.js
• Raphaël
• SWFObject
• Three.js
• EaselJS, part of CreateJS

Web-application related (MVC, MVVM, or otherwise)

• AngularJS
• Backbone.js
• Cappuccino
• Chaplin.js
• Echo
• Ember.js
• Enyo
• Google Web Toolkit
• JavaScriptMVC
• Knockout
• Rialto Toolkit
• SproutCore
• Web Atoms JS
• Wakanda Framework

Pure Javascript/AJAX

• FuncJS
• Google Closure Library
• Joose
• jsPHP
• Microsoft's Ajax library
• MochiKit
• PDF.js
• Rico
• Socket.IO
• Spry framework
• Underscore.js

Server-Side Related

• Node.js

Template Systems

• Cascade Framework
• Handlebars
• jQuery Mobile
• Mustache
• Twitter Bootstrap
• ZURB Foundation

Unit Testing

• Jasmine
• Unit.js

Source: 
http://en.wikipedia.org/wiki/List_of_JavaScript_libraries
http://en.wikipedia.org/wiki/Comparison_of_JavaScript_frameworks