The Easel Javascript library provides a full, hierarchical display list, a core interaction model, and helper classes to make working with the HTML5 Canvas element much easier.
The Swiss Army Knife of Vector Graphics Scripting – Scriptographer ported to JavaScript and the browser, using HTML5 Canvas. Created by @lehni & @puckey
A Javascript library for working with Audio. It provides a consistent API for loading and playing audio on different browsers and devices. Currently supports WebAudio, HTML5 Audio, Cordova / PhoneGap, and a Flash fallback.
PreloadJS makes preloading assets & getting aggregate progress events easier in JavaScript. It uses XHR2 when available, and falls back to tag-based loading when not.