I really like contributing to Open Source Projects. This page summerizes the projects I've contributed code to. It's not a comprehensive list (you'll need to check GitHub, GitLab, and a few other places for that) but it is a list of the contributations that are most important to me. This page does not list my personal projects, those are listed on the projects page.
From time to time I contribute code to the Ruby on Rails web framework.
I've contributed some updates to forumlas and casks for Homebrew, the missing package manager for macOS.
For a while I contributed code to FluxBB, simple forum software written in PHP.