According to the Team Fortress website, Steam will be allowing the trading of in-game items as well as Steam gifts in a new option that will attach to your community profile. The option is currently in Beta, but Steam is encouraging users to sign up (which is easy) and leave feedback.
Coming on the heels of the news that Diablo will allow real-life auctioneering of in-game items, something that may have heavy economic implications for the gameplay, that Steam is offering trading in this (free) capacity encourages not only an expanded gaming community, but a potentially even playing field. The trading option also allows for users to ‘gift’ games purchased on Steam that have yet to be added to their Library. Team Unwinnable suggests you head over to the TF site and try this out; you just might toss back a few Crit-a-Colas with Chuck.