Steam Trading Cards are now live. Go get'em!
Have made $20 in steam credit from going out and gathering cards... then selling them on the steam market.
And... I love it. :-D
/If there was a game associated with it I would be addicted. Without a game... it's just trading cards for steam achievements. Would rather take the $0.25 per card thank you. Got $2.50 for a rare card!