Commit Together by Github - Now add co-authors to your commits
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Commit Print - Posters of your git history
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Macarons - Macarons is your virtual watercooler for casual conversations with colleagues you rarely meet on the hallway.
Zube - Project management for developers.