Steam Trading, which allows players to trade in game items and gifts, has left beta. New titles are also being added to the service.
Sega's Spiral Knights joins Team Fortress 2 in allowing gamers to trade in game items and games, if that game has been purchased from the platform as a gift or an "Extra Copy".
The official FAQ also reveals that the service will soon extend to Portal 2, along with a number of third-party games.
"The addition of Steam Trading is the latest example of how Steam continues to evolve with new features and functions developed based upon feedback," said Valve's director of business development Jason Holtman.
"We look forward to seeing how gamers and developers have fun and move this functionality forward."
More information can be found on the official support site.
Over one million items and games were traded during the service's four week beta stage.