I'm running a community portal network that consist of online communities that people have created for free.
On each site we have either a 100x100 or 468x60 banner. We have a bit more than 200 communities at the moment and are getting around 3000 banner impressions per day.
Now I would want to banner trade with somone for a month to see if it could gain me more than my current banner trade program. You could get 1 to 4 slots (of 4 slots total) depending on how many impressions you generate.
I could also sell all the 4 banner slots for $150 for 1 month. (That is you get all the 4 banner slots for $150)