Ancient Coins. The Tantalus Online Coin Registry is a good idea. People can put up pictures, descriptions, and comments on their coins, and sell them there too. I guess once they're sold, they can stay on the registry, and they'd then be easy to re-sell, with a provenance established too, at least for a few years. It's great fun browsing there. And Roman coins are cheap. I found the site because I went to the British Museum today and found poor-condition Roman follis's for sale across the street for 2 pounds each.