GitHub Repository Size - Browser extension to show file and repo size in GitHub
APIs With GitHub - Create simple JSON APIs with GitHub Repository
replit - Code, create, andlearn together. Use our free, collaborative, in-browser IDE to code in 50+ languages — without spending a second on setup.
Sheety - Turn any Google sheet into an API instantly, for free. Power websites, apps, or whatever you like, all from a spreadsheet. Changes to your spreadsheet update your API in realtime. Neat
GitPress - A blog writing tool based on GitHub, designed for developers
repostatus - Repostatus runs a sentiment analysis engine on various aspects of your repo in order to calculate the happiness of your repo.