Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Gource - Gource is a software version control visualization tool.
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Codeology - Open-source algorithm that visualizes GitHub projects
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
The GitHub Matrix Screensaver - Latest commits from GitHub visualized Matrix-style