Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Octoview - The missing preview feature for GitHub
xoscope - Xoscope uses the input of your Sound Card, EsounD and/or a ProbeScope/osziFOX and Bitscope-Hardware.
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
GHuser - Better GitHub profiles for everyone
DownGit - Directly download or create download links to GitHub public folders or files.