Ramsophone - A generative art/music machine. (Be sure to refresh!)
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.
Tinkersynth - Create and purchase unique generative art
Drawasaurus - Drawasaurus is an online drawing & guessing game you can play with friends or strangers.
Generative Art in Go - Learn the basics of algorithmic art with the Go language
LetsDraw.It - Guess and Draw, Drawing Battle, Pictionary, Copy picture - online drawing games where you can compare your skill with others.