gartic.io - Draw, guess, and win!
Drawasaurus - Drawasaurus is an online drawing & guessing game you can play with friends or strangers.
skribbl - Word guessing based on drawing.
LetsDraw.It - Guess and Draw, Drawing Battle, Pictionary, Copy picture - online drawing games where you can compare your skill with others.
iSketch.net - A thrilling pictionary online game in various languages.
SketchParty TV - SketchParty TV is a high-tech drawing game that plays a bit like Pictionary.