devmarks.io - Bookmarking for Developers
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
GitHub Repository Size - Browser extension to show file and repo size in GitHub
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Pinboard - Pinboard is a personal archive for things you find online and don't want to forget.
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.