Commit Together by Github - Now add co-authors to your commits
GitHub Marketplace - Tools to build on and improve your workflow
Commit Print - Posters of your git history
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Macarons - Macarons is your virtual watercooler for casual conversations with colleagues you rarely meet on the hallway.
Board for Github - A webview based GitHub project app with native features