If you haven't heard, Goozex is an online used video game trading peer to peer network.  If you are interested in buying used games, and they have everything from PSOne to the current generation, then this is a great site.  You register and add the games that you will be willing to trade/sell and they are assigned point values.  After completing a trade, you get points based on that game which you can then use to buy other games.  It's a nice system that I hope to see grow in the near future to include older games going all the way back.  Check it out!  You won't be sorry!