White Label by Studio - Sell white label services under your brand
Smaller - Make your websites load faster
Holly Website Audit - Free, brandable website audit for your potential clients
Website Grader - Grade your website's strengths and weaknesses in seconds.
Ocoya - Canva + Hootsuite + Copy.ai
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.