GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Octoview - The missing preview feature for GitHub
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
Dyllo - A clean and simple way to view a Github user's information
Enhanced GitHub - :rocket: Chrome extension to display size of each file, download link and copy file contents directly to clipboard - softvar/enhanced-github