You could have a identifiable feed URL. Static, personalised ads that most feed readers wouldn't block.

And in terms of technology, there's nothing stopping you sticking an iframe or script block in your feed. It comes back to what the reader will allow. Origin really doesn't matter too much.

If you use a web reader, I think you don't even need an unique url if your ads are static images. Just request an image from your server and use the user cookie for recommendations