Drawception - The browser-based party game that combines the telephone game with drawing! Hilarity ensues.
DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.
Drawesome.uy - Offers both Drawing & Guessing games as well as collaborative drawing lobbies.
Aggie.io - Draw a picture together with your friends in real-time over the internet in your browser.
iSketch.net - A thrilling pictionary online game in various languages.
Panel Jam - Collaborate with others on comic strips