VectorWiki - A huge repository of ~120K brand logos in SVG format for free and quick download.
GraphicsJS - Free open-source JavaScript library for easily drawing HTML5 graphics and animation.
Brands of the World - Open source database of brands vector logos
altcanvas - Altcanvas is a project for developing a new and more intuitive GUI framework for handheld devices.
BonsaiJS - A lightweight graphics library with an intuitive graphics API and an SVG renderer.
Paper.js - Open source vector graphics scripting framework that runs on top of the HTML5 Canvas.