Here’s a nifty, free tool that will help find the most popular content online and the influencers who are sharing it BuzzSumo. All you do is enter a topic, domain name, or user ID and you will get results showing you the top related content or influencers.
BuzzSumo social search engine is designed to find the most shared content for a topic, author or a domain. For content, you can filter by some preset time spans and by type of content. For influencers, you can select one or more different categories of content providers.
The site offers case studies for the most common uses: