skribbl - Word guessing based on drawing.
Drawesome.uy - Offers both Drawing & Guessing games as well as collaborative drawing lobbies.
gartic.io - Draw, guess, and win!
SketchParty TV - SketchParty TV is a high-tech drawing game that plays a bit like Pictionary.
Drawception - The browser-based party game that combines the telephone game with drawing! Hilarity ensues.
iSketch.net - A thrilling pictionary online game in various languages.