Steam Trading is now enabled for Portal 2 and Spiral Knights, as well as Team Fortress 2.
Valve has officially bought the Steam Trading beta to a close, rolling out the full service across Steam for Team Fortress 2, Spiral Knights and Portal 2.
Steam Trading allows users to agree on swaps for in-game items and Steam Gifts with other players.
The open beta for Steam Trading, which ran last month, only supported Team Fortress 2, but now more titles are supported.
Valve has said it is working with other developers on rolling the service out to more games on Steam, though Sega's Spiral Knights is the only non-Valve game to support trading at launch.
A Steam Trading FAQ
has been posted by Valve and offers a full run-down on how the service will work.
Let us know your thoughts in the forums