SEO Analyzer By Neil Patel - A free SEO analyzer for your site
Serpstat - Search analytics, Rank tracking, Backlink analysis and Site Audit tool.
SEO Minion - Chrome extension & Firefox add-on to help you with SEO
SE Ranking - All-in-One cloud-based SEO software for agencies, marketing teams and webmasters
Curatedseotools.com - Curated directory of the best SEO tools.
SEOmator - SEO website analysis & audit tool