I buy old VW diesel engines, and then sell the parts on a couple VW diesel forums. I buy an engine every month or so, and then do a big sell-off a couple times a year.
I've found the only way to do it is to take lots of pictures, and have a well organized ad/posting. I usually update the original post as items are bought/sold... instead of just posting again on the thread. I try to be very conservative when describing items... point out ANY issues, even trivial ones. People have more confidence buying like that.
example:
http://vwdiesel.net/phpBB/viewtopic.php?t=6767&postdays=0&postorder=asc&highlight=sale&start=0