Tweebay.com, a recently launched site, uses the connectivity of Twitter links with an optional selling and buying format through auctions or 'buy it now' functions.
I am test driving Tweebay today. I added one book; it seemed easy enough to post a listing. It’s ground floor, but I will report back if it develops into the next best thing since sliced bread.
Grass doesn’t grow under my feet, and I love to share.
Let me know if you try it, I am curious as to all results.