Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Slack Themes - Make your Slack pretty with custom themes
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
Sweet Themes - Color Themes for Slack
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
Limnor Studio - It is a generic-purpose no-code programming system.