Seolyzer - Seolyzer is the ultimate SEO tool that provides you with all the information you need to improve your website’s health and performance.
Ubersuggest - Want more traffic? Ubersuggest shows you how to win the game of SEO. Just type in a domain or a keyword to get started.
SEOmator - SEO website analysis & audit tool
Keyword Explorer by Moz - Find the best keywords to improve your website's SEO traffic
Whatsmyserp - Powerful Rank & Serp Tracking. Completely Free.
Content Marketing Stack - A curated directory of content marketing resources