Hi, i created a very simple forum that is meant to help build the community of your forum.
The forum is called: Simple Machines Forum Ad Share. http://smfas.co.cc/index.php (http://smfas.co.cc/index.php)
The forum allows members to trade, buy and sell ad space.
It is a new forum, i just got the idea and made it. It is completely free to use. All you have to do is make a topic in the category you want (e.g. to trade ad space) and then people will reply to you and give you their ad (banner) to place on your website and they will place your ad (banner) on their website.