Curatedseotools.com - Curated directory of the best SEO tools.
Meta Tags - Meta Tags is a tool to debug and generate meta tag code for any website.
SEO Marketing Hub - Learn SEO for free
Screpy - Screpy is a web analysis tool that can analyze all pages of your websites in one dashboard and monitor them with your team. It's powered by Lighthouse and it also includes some different analysis tools (SEO, SERP, W3C, Uptime, etc).
SEO Minion - Chrome extension & Firefox add-on to help you with SEO
Rank Math SEO - A FREE powerful and lightweight SEO plugin for WordPress