Valve love the idea of trading so much, that they have released the beta version of a system that allows players to trade unplayed games with one another for other games and in-game items.
Imagine what you do in TF2 – you poke someone, offer them your goodies for their goodies, and go off on your merry way. That’s how this is gonna work, but through Steam – this also means you no longer have to boot up TF2 to trade as well, all trades done in the friend list. However, any games that have been played will not be able to be traded, so extra copies as part of a bundle or just games you never got to start up are the only ones you will be able to choose.
At the moment, it’s only TF2 but this may extend to other games, especially the other F2P games. To get into the beta, just go to your Steam Settings, and activate the Beta from there. All the information is on the Steam Support page for the Beta
(Source: GamePro )