AngularJS
is what HTML would have been if it had been designed for building web applications. It provides your application’s plumbing so you can focus on what your app does, rather than how to get your web browser to do what you need.
FireQuery
jQuery expressions are intelligently presented in Firebug Console and DOM inspector
attached jQuery datas are first class citizens
elements in jQuery collections are highlighted on hover
jQuerify: enables you to inject jQuery into any web page
SoundManager 2: Javascript Sound for the Web
SoundManager 2 is an attempt at providing the sound API which Javascript has been missing. It's a Javascript library which wraps and extends Flash's sound capabilities, bringing cross-platform audio functionality to Javascript.
Jiffy Firefox Extension - Documentation
The Jiffy Firefox Extension is written Bill Scott of Netflix. It adds an additional panel to Firebug that provides a visual view of the Javascript time measurements captured by Jiffy-Web. The extension is available under Creative Commons license.
Regular expression tool - regex.larsolavtorvik.com
Developing an accessible slider | Filament Group, Inc.
The solution we devised is based on the core principle of progressive enhancement: start with basic, functional markup and then layer on complexity, if supported. In most cases, coding for progressive enhancement allows us to build a single code base for both the basic and enhanced versions; we then apply additional CSS and Javascript to create the richer experience for capable browsers. But when we're developing the UI for a web application and creating widgets that capture data, we're often starting with form element markup that doesn't readily cooperate with CSS, or that doesn't have all the moving pieces necessary to create a more complex widget.
pi-js - Google Code
pi.debugger is a cross browser web development tool allows you to examine web page's structural and debug with console.
Greg Sherwood: PHP_CodeSniffer and JavaScript Lint
The new JavaScript tokenizer in PHP_CodeSniffer allows you to write your own custom JS sniffs, but JavaScript Lint already has a set of generic tests that can be applied to your code. Thanks to the JavaScript Lint command line tool, jsl, you can now include JavaScript Lint warnings and errors in your coding standards.