If you run a blog or a site that offers RSS updates, you might want to consider making your content available via email

There are several services available for this, and one of which is Feedblitz. You can either manually create your email newsletters - or get auto updates using your RSS feed

they also run a Feedblitz Ad Network, where people can buy advertising space in various mailing lists. And, those newsletter publishers who run these ads can earn some revenue from such advertising

Feedblitz Ad Network info

FeedBlitz’s email advertising programs enable advertisers to place targeted ads in newsletter updates, and bloggers and newsletter publishers to make money from (or “monetize’) their mailing list. It is an entirely self-serve and opt-in solution

There are different variables to the earning capabilities of this program.
1) Free users are able to participate, but Premium users are given double earnings/revenue share.
2) List size (number of subscribers) will also affect your earning capabilities, as the number of times ads are viewed and clicked will have different effects.
3) The number of times you publish content via Feedblitz will also affect the earnings.

There’s also $25 payment threshold. Once that amount is reached, payment will be made 45 days later payment via paypal only