GitHub.io is a popular platform for hosting "unblocked games" because it uses the GitHub Pages service, which is often not categorized as "Games" by school or workplace web filters. These sites typically host lightweight HTML5 and Flash (emulated) games that run directly in the browser.
If you're looking for a one-stop-shop, these repositories and sites are among the most frequently updated: 1. Github Games (git-hub-games.github.io) githubio unblocked games top
GitHub.io unblocked games are browser-based gaming sites hosted via GitHub Pages Top Categories of Games Found on GitHub