skribbl - Word guessing based on drawing.
gartic.io - Draw, guess, and win!
Drawasaurus - Drawasaurus is an online drawing & guessing game you can play with friends or strangers.
LetsDraw.It - Guess and Draw, Drawing Battle, Pictionary, Copy picture - online drawing games where you can compare your skill with others.
Aggie.io - Draw a picture together with your friends in real-time over the internet in your browser.
Cast-a-Draw - Pictionary style party game for Chromecast on Android