http://teamfortress.com/post.php?id=6040
https://support.steampowered.com/kb_article.php?ref=6748-ETSG-5417
Shame you can't trade off used games, but otherwise it sounds pretty cool.
As we all know, Jonas Salk invented money in 1955 so he would have a way to earn a living from his polio vaccine. Before that, people just traded things they found for things that other people had found. So you might "sell" somebody a scrap of carpet, say, in exchange for an old bottle. It was a perfect system with only one drawback: people spent their lives bartering for piles of garbage before dying of polio.
But wait. What if we told you that you could barter for things that weren't garbage, AND not die of polio? Steam Trading Beta lets you securely trade your in-game items for other in-game items from participating games. You can also trade Steam gifts (games on Steam that you've purchased but not yet added to your Games Library).
Want to try it out? In Steam, go to Steam > Settings, and opt into Steam Trading Beta. That's it! Now your Steam Community profile will have an item inventory, and you'll be able to view the item inventories of every public profile in the Steam community.
Now that you've opted into the Trading Beta, you can invite people to trade through Group Chat, and trade with anybody in your Friends List who's also opted in. Just right-click on their name and select "Invite to Trade" from the dropdown menu. Once your friend accepts your offer to trade, a trade window will open up. The first time you open the trade window, a step-by-step walkthrough will guide you through your first trade.
That's it! Opt in and get trading, or surf over to the Trading Beta FAQ for the nuts and bolts. And remember: Trading is still in beta, so don't forget to give us your feedback here on the Forums.
https://support.steampowered.com/kb_article.php?ref=6748-ETSG-5417
Question
What is Steam Trading, how does it work and how do I participate in the beta?
Answer
How do I get into the Steam Trading Beta?
From the Steam Client, open Steam->Settings and select the Steam Trading Beta option. The Steam Client will then need to restart in order to download and apply the change.
What items can be traded?
Team Fortress 2 items and Steam Gifts can currently be traded in the Steam Trading Beta.
Will there be other games that support trading?
Were working now with other game developers to incorporate both Trading and Inventories. Portal 2 should be reasonably soon and we hope to have several third-party games in the next few months.
What do you mean by trading Steam Gifts?
Any game youve purchased from the store as a gift, or received as an Extra Copy, can be traded to other users. They can be used to trade for other Gifts, or for items in Team Fortress 2. Weve added a new checkout option to the Store when purchasing a gift so you can save it for trading or sending later, to support users who want to save games for trade fodder.
What restrictions are there on trading Steam Gifts?
Trading a Steam Gift is very similar to sending a gift to someone; just that once it is traded that user can then either trade it again, or open it for themselves. There are no restrictions on territory.
Does Steam Trading mean I can sell my used games?
No, only games that have been bought as a gift, and thus have never been played, can be traded. Once the Steam Gift is opened and added to your game library, you wont be able to trade it again.
How do I see my Inventory on the Steam Community?
Once you have opted in to the Steam Trading Beta, you can select Community in the Steam client, then on the right is a link to View Inventory.
Who can see my items?
Your inventory obeys your existing regular privacy settings public, friends only, friends of friends, or private.
Who can I trade with?
Right now you can initiate a trade with anyone in a Group Chat or on your Friends List who has also opted into the Steam Trading Beta.
How is this different from trading in Team Fortress 2?
Weve improved the display of changing which items are in the trade, and significantly increased the number of items that can be traded in one session. We hope these improvements will help with confusion or users trying to deceive others in the trade.
I have ideas for other things in Steam that can be traded. How do I give that feedback?
Weve set up a forum thread here where you can post all feedback relating to the beta.
I have found a bug in Trading, how do I report that?
Please report all bugs in the same forum thread for giving feedback. Please click here to go to the thread. We will be actively reading the thread during the beta.
I think I just lost items in a trade! What do I do?
Youll need to Contact Steam Support and create a new ticket. Please include your account name or a link to your Steam Community profile in the Support Ticket, as well as all the details you can remember from the trade. It will also be helpful to include a list of items that you have lost, a link to the Steam Community profile of the user that you traded with and the date and time of the trade.
Whats this new Friends Tagging feature?
Its not related to trading, but in this new Steam Client is also a new feature to help you organize your friends list. You can right-click on any friend and select Tag As to choose a category for them. Friends can be tagged in multiple ways, and will show up then several times in your friends list, once for each tag.
Shame you can't trade off used games, but otherwise it sounds pretty cool.