A scalable, hosted API for realtime push messaging for Web and mobile apps, that is powered by HTML5 WebSockets. The pricing looks pretty good too.
JavaScript
Sinon.JS
“Versatile standalone test spies, stubs and mocks for JavaScript…No dependencies, works with any unit testing framework.”
Ascensor.js
via @adammmccombs A jQuery plugin that works in conjunction with the ScrollTo plugin to provide an interesting set of scrolling + full screen capabilities.
Chosen
A “JavaScript plugin that makes long, unwieldy select boxes much more user-friendly. It is currently available in both jQuery and Prototype flavors.”
Smoosh
via @joemccann
A command line tool “for packaging your CSS & JavaScript projects. It will lint your JavaScript with JSHint, then build and minify your files (if you’d like) with UglifyJS for JavaScript, and Sqwish for CSS.”
How to build a web widget (using jQuery)
via @garannm