I use a couple of established game-swapping sites, and I've had good experiences with both.
gametz.com lets you list the games you want and the games you have available, then matches you with other users that you could trade with. The two of you then work out the details of the trade on your own.
goozex.com uses a more communal system, rather than matching people up for one-on-one trades. When you send a game to any other user, your account is credited a certain number of points, and you can then trade these points to any other user for any other game.
Both sites have reputation systems, so you know whether particular users can be trusted.







