Masonry
Layout elements in a grid, like a mason fitting stones in a wall
Moment
Parse, validate, manipulate, and display dates in javascript.
Modernizr
Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.
Mousetrap
Simple library for handling keyboard shortcuts in Javascript
Morris.js
Pretty time-series line graphs
Mustache.js
Minimal templating with {{mustaches}} in JavaScript
Numeral
A javascript library for formatting and manipulating numbers.
Normalize.css
A modern, HTML5-ready alternative to CSS resets (as used by Twitter Bootstrap, HTML5 Boilerplate, TweetDeck, Soundcloud, and many others).
Noisy
A jQuery plugin that adds random noise to the background of a given element.
Paper.js
The Swiss Army Knife of Vector Graphics Scripting – Scriptographer ported to JavaScript and the browser, using HTML5 Canvas. Created by @juerglehni & @jonathanpuckey
Ocanvas
JavaScript library for object-based canvas drawing.
Postal.js
JavaScript pub/sub library supporting some advanced subscription features, plus message capture and replay
Platform.js
A platform detection library that works on nearly all JavaScript platforms.
Placeholder Shiv
Tiny polyfill for the placeholder form element attribute. Requires Prototype.js.
Path.js
Simple, lightweight routing for web browsers
Prototype
Prototype JavaScript framework