Well actually Buy, Sell, Swap... Windows Live Expo is now in public beta:

"Expo is more than just your basic buying and selling - there are loads of features which make the process quicker and easier. And now with the move to a pubic beta, there are even more people visiting the site; which means more content to explore and better opportunities to sell your stuff. And remember, it's all free!

With Expo you can:

  • Trade exclusively with those you trust, like your colleagues or schoolmates, using Expo Communities.
  • Search for items locally or across the UK using the integrated Windows Live Local maps.
  • List items quickly and easily, and most importantly, for free!

http://uk.expo.live.com

Since this is a public beta there are no invitations or waitlist, so click the link above and get started buying and selling!"