I doubt goozex is the one you're looking for, but I do recommend it. It works a little differently than you describe though.
W/ goozex you put your games up for 'sale' and they're worth a certain amount of points. When somebody requests that game you get an email to accept it, then they give you the address to send it to. When they confirm they got it you get your points... once you've traded enough you no longer have to wait for your points, and you get them once you confirm you shipped it.
You constantly add games to your 'wants' list and it puts you in line to get the game. When you have enough points for a game it'll try to match you up with a seller if you're near the top of the list.
One caveat, you also need 'trade credits' to request a game which cost money to goozex. They're $1 a piece (discounts for bulk buys) which is a small price to pay for them to keep the site going IMO.
I've sent 20 games and received 8 over my 1 1/2 year or so there, and I've only had 1 time where the guy never shipped me the game. After starting a claim though they gave me my points back within a week.