Pdfmake
Client/server side PDF printing in pure JavaScript
Ladda
Buttons with built-in loading indicators.
Jo
Jo is a thin (~12K) candy shell for PhoneGap apps. It's an HTML5 mobile app framework which provides UI widgets, a flexible event model, a wrapper for sound, and a light data layer. Apps are skinnable with CSS3, and work everywhere PhoneGap does... and then some, including Adobe Air and OSX (desktop and dashboard).
Jasmine Ajax
jasmine-ajax - A library for faking Ajax responses in your Jasmine suite.
Hammer.js
A javascript library for multi-touch gestures // You can touch this
Fastclick
Polyfill to remove click delays on browsers with touch UIs
Bacon.js
FRP (functional reactive programming) library for Javascript
Almond
A minimal AMD API implementation for use after optimized builds
Alchemy
Alchemy.js is a graph drawing application built in d3.
Aja.js
Ajax without XML : Asynchronous JavaScript and JavaScript/JSON(P)
Smooth State.js
Unobtrusive page transitions with jQuery.
Jquery.payment
A general purpose library for building credit card forms, validating inputs and formatting numbers.
Retina.js
JavaScript and LESS helpers for rendering high-resolution image variants
Imagesloaded
JavaScript is all like "You images done yet or what?"
Twig.js
JS implementation of the Twig Templating Language
Stampit
Create objects from reusable, composable behaviors.
Modernizr
Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.