This is a great little website that is similar to the drawing game "Pictionary" that I'm sure you've all played at some point in your life.
Players take turns to draw a word (or words) or words while other players try to guess. Players earn points once they've guessed the word. This is an addictive time waster and free to play, no registration is required. I recommend reading the game instructions and rules because they're fairly strict on what you can and cannot draw in your pictures.