Here are two interesting items. The first is from Burkhard Schipper, an economist at the University of Bonn. He created a game where you play as a firm against other firms and find out how you did against the computer and how you stand relative to other players. It takes about 5 minutes.
Talking of internet games, I came across something that is really spooky. I cannot figure this one out. I am pretty clever but that one has me totally puzzled.