gartic.io - Draw, guess, and win!
FlockMod - Flockmod is a free real time online group drawing app with all the bells and whistles.
skribbl - Word guessing based on drawing.
Doodle or Die - It's like the game of Telephone. Except with doodles.
Drawasaurus - Drawasaurus is an online drawing & guessing game you can play with friends or strangers.
iSketch.net - A thrilling pictionary online game in various languages.