Webchemy

Webchemy is an open-source cross-platform web-app for creating idea sparking sketches. Based on the desktop application Alchemy, Webchemy takes some of its drawing tools and brings them to the web. Webchemy is great for generating new ideas, but at some point it's better to take your concepts and let them evolve within other tools. That's why you can export your creations as PNG and SVG (Scalable Vector Graphics).