Moment.js : A javascript date library for parsing, validating, manipulating, and formatting dates.
TraceKit : Not all browsers support stack traces on error objects, but TraceKit squeezes out as much useful information as possible and normalizes it.
impress.js : It's a presentation framework based on the power of CSS3 transforms and transitions in modern browsers and inspired by the idea behind prezi.com
Frappe Charts : GitHub-inspired simple and modern charts for the web with zero dependencies.
howler.js : howler.js is an audio library for the modern web. It defaults to Web Audio API and falls back to HTML5 Audio.
A super micro tiny DOM library for authoring HTML5 mobile web applications.