tf2 tradeing just came out a few days ago would be nice to have a place to trade hats and items with other tf2 players on jsp
for everything about tradeing update its here
http://www.teamfortress.com/mannconomy/FAQ/TRADING & CUSTOMIZATION
Q: Will I be able to trade items?
A: Yes. We've added the long-requested Trading feature, so you can swap items with friends.
Q: Are all items tradeable?
A: No, not all items are tradeable. Some limited-availability items are not tradeable. Purchased items are also not tradeable at the moment (see About the Store).
Q: Can I customize my items?
A: Yes. In addition to our existing item customization, we have created new kinds of items that will enable a greater amount of customization than we've had in the past, like the ability to name items and even change their color scheme. The Mann Co. Catalog will let you find out which items are customizable and how you can customize them. We've also doubled the amount of backpack space available to you, so that you’ll have room to store all this new stuff.
Q: Can I just give items to someone? Or do they have to give me something back?
A: Yes, you can "gift" items to others. They do not have to give you anything back.
Q: Can I craft the Polycount weapons? Do they have recipes like the other community items?
A: Yes, they're craftable. They have the same recipe style (combine two items) as the other community-contributed items.
from valve ^