I've just started playing PerplexCity - a puzzle contest cum collectable card game. You buy a foil package of cards (much like Magic: The Gathering, or - I guess - baseball cards). Each pack contains 6 cards, each with a puzzle on the front. When you've solved the puzzle, you can log in to their server and enter your answers. If you have it right (down to spelling and punctuation, grr), it'll be checked off, and you get a certain number of points.
As far as I can tell, points don't matter.
You see, the bigger game is that there's some "cube" that's gone missing in this fictional world, and by playing the game, you're gathering clues that should help you recover the cube. If you return the cube, you win $200,000.
As you can see in the picture above, puzzles are ranked in difficulty from red (easy easy) to green (moderately tricky) to purple (supposed to be hard) to grey (haven't seen one yet). You get more points the more difficult the puzzle is (to a degree - there are some purples that are pretty straightforward, from what I've seen). You can attempt to answer a given card 3 times in a 24 hour period, which discourages guessing, somewhat.
So, it's online, so if anybody else is playing, feel free to track me. Also, it's collectable, so you might have extra cards you want to trade away. Also, if you want help spending $200,000, let me know.