Website Grader - Grade your website's strengths and weaknesses in seconds.
Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.
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.
Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.
PageSpeed Ninja - One-click page speed boost for WordPress
RabbitMQ - RabbitMQ is an open source message broker software.