Banner Ad rotation script recommendation?

I have some affiliate programs and would like to just put together a simple rotation scheme for my homepage and a few other key pages on my website. Anyone have any suggestions? Prefer to keep it to flat file so not hit the db for this. Perhaps in future I'll do db programming, putting images into blob. But for now all I'm looking for is simple and effective script for flat file. When page loads it will grab one of a collection of banner ads and place that in my div.

Thanks. (& go NY Giants!)