Valve has launched the Steam Trading Beta, a new system that allows users to trade Steam Gifts and in-game items.
The beta currently only applies to Team Fortress 2, but, according to a FAQ on Steam, " Portal 2 should be reasonably soon and we hope to have several third-party games in the next few months."
Along with in-game items, any game purchased in the Steam Store as a Gift, or received as an "Extra Copy", can be traded with other users. Only unopened Gift games will be accepted in the system.
A new checkout option has been introduced to the Steam Store that allows users to save a Gift for trading at the point of purchase.
The news follows Blizzard's introduction of an auction house in Diablo 3 that allows players to sell loot for real currency.