OpenHub for GitHub - Fast and concise, open-source GitHub client app.
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.
Wuffle - A multi-repository task board for GitHub issues.
Zube - Project management for developers.