I think [WTT] tag fits more your title. since it's an exchange - trade.
anyhow, for how long?
I'm feeling in a good mood today and i'm allowing 3 banners 125x125 on my site:
Under the sponsors sidebar will enable 2 more adspaces to make 4 free spaces
Most likely will accept any site's that will do the same in exchange and your banner must look good