To aid you in finding a co-op partner, all current owners of Portal 2 will receive a Steam coupon for 75% off a copy of Portal 2, which can be given away to other Steam users. Check your Inventory for details!-- Valve at the Portal 2 store page on Steam.
Guys, this is a seriously good deal. Portal 2 is an excellent game.
I've given the coupon to shanaqui! Hope you enjoy it. :)