Paper.js - Open source vector graphics scripting framework that runs on top of the HTML5 Canvas.
altcanvas - Altcanvas is a project for developing a new and more intuitive GUI framework for handheld devices.
p5.js - JS library for creating graphic and interactive experiences
Pixi.js - Fast lightweight 2D library that works across all devices
FabricJS - Fabric.js is a powerful and simple Javascript HTML5 canvas library,
Three.js - A JavaScript 3D library which makes WebGL simpler.