This is kind of neat, has anyone heard of this?
http://www.swapstyle.com
It's like ebay, only you can negotiate to trade instead of purchase. You list a bunch of items you are willing to swap, and when you see something you like on someone else's list you offer to let them swap that item for one of yours.
They do more than clothing, but I thought the clothing thing was really neat. I just joined, so I haven't actually swapped anything yet, but I have been trying.