Observable - Interactive code examples/posts
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.
nbviewer.org - Rackspace server host Jupyter Notebooks from your github repo
Kajero - Interactive JavaScript notebooks - create good-looking, responsive, interactive documents.
Calculist - The open-source, web-based thinking tool that facilitates effective thinking for solving problems.
Binder - Turn a Git repo into a collection of interactive notebooks