BuzzSumo

BuzzSumo is a content research and monitoring tool that identifies the most shared and engaging content for any topic or competitor. Key features include Content Discovery, Influencer Identification, Question Analyzer, and Backlink alerts.

While its core is social/content trends, it's invaluable for SEOs to find popular content ideas and link-building opportunities. Targeted at content and digital marketers, plans start at $199/month. It ranks for its unique focus on content performance beyond search, its extensive database of social shares, and its utility in crafting a content strategy that earns both shares and links.