Bootstrap (front-end framework)
Bootstrap (front-end framework) has been used by MSNBC and NASA and a most popular project on GitHub. It is a free tool for designing templates according to the device.
Mustache (template system)
Handlebars (template system)
Handlebars is written by Yehuda Katz in 2010, a semantic web template system. It can be used to render Mustache templates. It also has some logic same as Mustache, such as #list, #with, #unless and more.
MVC, MVVM, or otherwise
Google Web Toolkit
Echo (framework) was primarily create to leverage the Swing object model (SOM) to improve the speed of application development. You can avail this software under the terms of MPL.
Cappuccino (application development framework)
Chaplin.js framework is written in JavaScripit and developed by Ryan Leckey, Paul Miller, Mathias Schäfer and Chaplin.js contributors. It is based on MVC. This framework uses “Backbone.js” library and best for single-page applications.
Backbone.js library is written by Jeremy Ashkenas. It comes up woth a RESTful JSON interface and based on MVP (model-view-presenter).
Canvas or SVG related (Graphical/Visualization)
Processing.js was written by John Resig in 2008, designed to write interactive content, images and visualizations. If you don’t want to use Java applet or Flash plugin for displaying graphic rich content, then use Processing.js.
Kinetic.js is used to extend the 2D context by enabling high performance event detection of mobile or desktop applications.
GUI-related (Widget libraries)
Webix is collection of various UI widgets that cover the most required elements of enterprise applications. These extensions allows you to embed your additional functions into your new enterprise applications.
SmartClient Ajax framework was released in 2001. It is a collection of GUI components, meant to allow applications to be created without directly messing up with HTML or using low-level Ajax techniques.
script.aculo.us is written by Thomas Fuchs. It provides user interface elements and dynamic visual effects via the DOM.
jQuery UI is built on top of the jQuery, provides themeable widgets, advanced effects and animations.
IX Framework uses technologies, such as DOM scripting, DHTML and Ajax for building rich web applications.
Ext JS is developed by Sencha Inc. It is an extension of YUI library which includes interoperability with Prototype and jQuery.
YUI Library (Yahoo! User Interface Library) uses DOM, DHTML and Ajax scripting with several core CSS resources.
accDC is the first of its kind Accessibility API for the web. Written by Bryan Garaventa FRSA in 2010. Featuring flexible namespaces, dynamic extendability, event handling, CSS target zones, flow control methods, screen reader, Ajax processing, Behavior modifiers and AccDC Object traversal.