I have made some research and I have found the following Outbrain competitors:
SmartGenies
Interactive Content Creation and Distribution Software
OneSpot
Unleash your content to drive business results.
idio
Maximize the value of your content marketing
Gravity
Our goal is nothing less than creating magical personalized experiences for you across the entire web.
Zemanta
About Zemanta
Content Ads, Amplified & Optimized
Docurated
Docurated accelerates sales in companies looking for fast growth by making the best Marketing content readily available to Sales around the world.
Content Runner
Connect with writers and organize your writing projects in one place with our project management tools. Invite your own writers, create content and publish it on WordPress with our white labeled plugin. Track revisions and deadlines and if you get stuck coming up with content topics, use our Idea Engine to help spur your creative juices!
Taboola
Distribute Your Content. Premium Publishers. Engaged Audiences.
Distribion
Focused exclusively on helping distributed marketing organizations improve their marketing and sales performance.
Beegit
The content-first project management solution for teams of all sizes
Cinevee
Sustainable Entertainment. Load your film. Tell your fans. Get Paid!
Rallyverse
Rallyverse is a SaaS content marketing platform that helps teams discover, create and share great content.
Here is another very useful article that has helped me very much.
www(dot)techgyd(dot)com/outbrain-taboola-nrelate-gravity-content-recommendations/4924/