Some auction sites prohibit any upselling or affiliate type of links inside the auction ad. Keep in mind you get to play the part of a merchant. I think this is very valuable. You get to reverse the role and see what it is like to actually close and deliver the sale. It is not as easy as it looks.
Many small businesses are ready to strike an alliance.
Power sellers see and talk to a lot of people. This is the easiest way to get the word out about your site. Advertise your excess banner inventory at auction. Make sure your auction is stuffed with keywords that relate to your site. As a bonus you may sell excess inventory and make new advertising connections.