We do have an online classifieds section that is open to individual members as well as retail and mail order stores:
http://www.finescale.com/fsm/classifieds/default.asp
The ad rate per month is $0.35 per word, $10.00 minimum so it's quite reasonable.
If you're asking about a free forum for buying, selling, and trading, that is a question that comes up with some regularity here and, while it does continue to be discussed, I don't anticipate a change in the corporate policy prohibiting it anytime soon.