Swapstack but for Websites? More simple ad service?

Swapstack is a great service to get paid sponsorships if you have a successful newsletter.

Are there any similar services for websites? Something as easy as listing ad/promotion spaces on your website, and anyone can "rent" those spaces for a limited period of time. Like with traditional ad networks, but without all the complicated tracking, loading third-party libraries, displaying random ads, and all that hassle.

Anybody aware of such a service? Or maybe it's time for one?