Ahrefs Backlink Checker - With the world's biggest index of live backlinks (over 15 trillion), Ahrefs Backlink Checker will show you the most complete backlink profile for any website.
Checkbot - Checkbot will boost the SEO, speed and security of your site by checking you're following 50+ web best practices. Browser extension with free and paid plans.
Backlinks by Neil Patel - A backlinks research tool for competitive intelligence
Google SERP Snippet Optimization - SEOmofo tool replicates the appearance of a snippet in Google SERPs, which allows SEOs to optimize a page title and description for maximum click-through rate.
SEMScoop - Find and analyze easy to rank long-tail keywords with free SEMScoop Keyword Difficulty Tool, Start using them for SEO, PPC, content creation and all your marketing activities
PrepostSEO Guest Posting - Daily Updated (10-30 sites added daily)- Publish Guest Posts at high authority guest posting sites (blogs). All premium websites listed.