GitHub + Slack Integration - Full visibility into your GitHub projects right inside Slack
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Cryotos - #1 Maintenance Management Software
Octoview - The missing preview feature for GitHub
Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.
Dyllo - A clean and simple way to view a Github user's information