We've been promoting our sponsors and content recently with Taboola, a contextual promotion platform where our feed is read and the articles are aligned on other relevant publications throughout the web. We're happy with the finite control over distribution and cost per lead through the program – plus their staff has been great.
We moved to Taboola after using another service that accidentally disregarded our budget and then wanted us to pay for $10,000 worth of distribution they provided us. Perhaps the dumbest part was that one of the articles they wanted us to pay for promotion on was an article about them! Umm… nope.
Another advantage of Taboola was that we could utilize both a list of static articles we wished to promote as well as utilize our feed to continue to promote our newest articles. Very cool indeed. This means we could promote articles about our sponsors, our most popular articles, as well as get some traffic on recent articles.
Interestingly, even if you enable featured images in WordPress, that doesn't modify the RSS feed of your WordPress blog to include those thumbnails in your RSS Feed. I think that's a gap in functionality that WordPress needs to correct, but in the meantime there is a solution!
Ladislav Soukup has developed a plugin called SB RSS Feed Plus that enables you to embed your post thumbnail properly utilizing the correct RSS Feed media:content and enclosure tagging. Install and configure the plugin and you can specify the image as well as some additional parameters.