Kind of surprised no one else has posted this....http://store.steampowered.com/holidaysale/details
So, basically Valve is doing this thing where you complete achievements (maximum 6 per day), and for each achievement you get a 'gift'. A gift can be: A game, a coupon, or a lump of coal, and they can be freely traded with other users. Now one (1) of these achievements, every day, is free, in that you don't have to have a pay-for game to earn it (brilliantly fiendish of Valve, btw). Although, all I've gotten from those so far, is coal.
Seven (7) units of coal can be turned into another gift, or you can use each lump of coal as an entry into a lottery/giveaway (note: you must have ten (10) items in your wishlist to qualify for the giveaway) for fabulous prizes.
I made this so that we can list what we have and what we would be willing to trade, and then do so.