Observable Notebooks - The portfolio and technical blog of Chris Henrick – provider of professional web development, data visualization, GIS, mapping, & cartography services.
codebunk - Realtime Collaborative Editor with Code Execution, REPLs and Chat
Jupyter - Project Jupyter exists to develop open-source software, open-standards, and services for interactive computing across dozens of programming languages. Ready to get started? Try it in your browser Install the Notebook.
Floobits - Floobits brings real-time collaborative editing to text editors, IDEs, and now Atom.
BeakerX - Open Source Polyglot Data Science Tool
coderpad - Collaborative code editor with in-browser, real-time execution. Conduct programming phone screens like a boss.