The public beta of Windows Live Expo has been released. This is Microsoft's answer to eBay and Craigslist. You can post items to sell or to buy and share the listings with everyone, your "buddies" or with people at work or in an organization. You can do the latter by restricting viewers from within selected domain names.
I'm testing it right now by listing some Robert Ludlum books that I want to sell. I restricted my listing to fellow employees.