I personally wouldn't be opposed to a "marketplace" sub-forum or at least a dedicated thread where people can post various memorabilia they no longer want... or are looking for. I doubt many people would frequent it, but ya never know. It might technically currently be against the rules to hock your Celtics jacket here, but I can't think of a more appropriate place... if you're lookin for hardcore Celtic fans, this is the spot.
Also, I try to avoid ebay and their fees whenever possible. I've had great success buying and selling stuff safely using paypal (random collectables in the $10-50 dollar range).