Marketing Island/System

I say there should be some kind of island that you goto and there is only a storage agent, and a trading agent. Sellers go there and place your item for sale and how much you want for it and you can leave. Buyers can go there and search for an item and find the lowest priced one someone put up for trade and buy it.

-Death

There's a ton of topics about this already, the so called "Auctionhouse".
Search for it

^ What Aera said.