SendView - The best way to track your competitors' email marketing.
Really Good UX - A library of screenshots for UX inspiration
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.
Usability.gov - Resource for user experience (UX) best practices & guides
Seolyzer - Seolyzer is the ultimate SEO tool that provides you with all the information you need to improve your website’s health and performance.
UX Check - Easy heuristic evaluations on your website (chrome ext.)