AWS Cloud9 - AWS Cloud9 is a cloud-based integrated development environment (IDE) that lets you write, run, and debug your code with just a browser.
GitHub Visualizer - Enter user/repo and see the project visually
Koding - A new way for developers to work.
SyntaxDB - Easily look up programming syntax for multiple languages
replit - Code, create, andlearn together. Use our free, collaborative, in-browser IDE to code in 50+ languages — without spending a second on setup.
Codeology - Open-source algorithm that visualizes GitHub projects