I think we should have a category like a mini eBay.
You post what you have with a picture, minimum bid and a cutoff date/time.
Buyers would IM you with their bid, at the cut off you would inform the buyer that they won and include your paypal address while requesting a shipping address.
( You would have the option of specifying in the original ad as to shipping being included or not )

Also if you are nice, you could IM the losers and say better luck next time, loser !