Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Nullboard - Minimalist locally-stored kanban board / task list manager.
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Huboard - HuBoard is built from the ground up using the GitHub public API.
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
Gitify - GitHub Notifications on your desktop.