GitHub Visualizer - Enter user/repo and see the project visually
GitHub + Slack Integration - Full visibility into your GitHub projects right inside Slack
Octohunt - Search to find developers in your city on Github.
Cryotos - #1 Maintenance Management Software
Gource - Gource is a software version control visualization tool.
Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.