KeepUpdated - Automatically track changes on any website online
LetsDraw.It - Guess and Draw, Drawing Battle, Pictionary, Copy picture - online drawing games where you can compare your skill with others.
Mini Metro - Make the trains run on time
skribbl - Word guessing based on drawing.
NewsDiffs - Tracks edits to stories over time on major news sites.
gartic.io - Draw, guess, and win!