SEMRush - All-in-one Marketing Toolkit for digital marketing professionals.
Whatsmyserp - Powerful Rank & Serp Tracking. Completely Free.
Moz - Backed by industry-leading data and the largest community of SEOs on the planet, Moz builds tools that make inbound marketing easy.
SEOmator - SEO website analysis & audit tool
SEOquake - SEOquake provides a browser extension to conduct on-page SEO audit.
Panguin Tool by Barracuda Digital - See your website's Google organic visit data overlaid with Google's major algorithm updates and changes to easily identify the impact on your website. Technology by Barracuda Digital.