Dropzone.js : DropzoneJS is an open source library that provides drag'n'drop file uploads with image previews.
Sammy.js : Sammy is a tiny javascript framework built on top of jQuery, It's RESTful Evented Javascript.
Web Forms : Web Forms 2.0 Cross-Browser Implementation
Workbox : JavaScript Libraries for adding offline support to web apps.
Zepto.js : Zepto is a minimalist JavaScript library for modern browsers with a largely jQuery-compatible API. If you use jQuery, you already know how to use Zept...
A simple library for handling keyboard shortcuts in Javascript.