Status Machine is a Web application that checks your website(s) to make sure it doesn't have critical problems that could affect your site's SEO, uptime or visibility.
It is currently in private beta, but let me know if you'd like to try it.
Open source software
I have many open source projects that I maintain, but the one that I love the most is Data Bible. It's an Open source Web application to study the Bible. It's written in Ruby on Rails and CoffeeScript and it supports many interesting features like parallel reading of many translations at the same time, and tagging of verses, to name a few.
Daily WordPress Documentation
It was a daily mailing list where I posted the short version of the documentation of a WordPress function. It included stuff like example usage, return value, expected parameters, etc. The list reached as much as 1100+ readers after a couple of weeks of sustained effort. It was a great way for people to slowly learn the WordPress API for creating themes and plugins, one email at a time.