www.madisonavenue.com - It's free, web-based ad rotation solution. We support Single TextAds (just one-liners) and Cluster TextAds (ad headline in bold, ad descrip below not in bold).
System is very powerful but easy to setup. You can use it to run any types of campaigns you want: affiliate, retail (ones you sell), internal/trade, and OPTIONALLY you can have us sell the traffic for you.
Hit me up and I'll run you through the system.