You Need A Wiki - Create a wiki with Google Docs
Observable Notebooks - The portfolio and technical blog of Chris Henrick – provider of professional web development, data visualization, GIS, mapping, & cartography services.
Stack Overflow Documentation - A crowdsourced developer documentation
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.
Docusaurus - Easy to maintain open source documentation websites
Calculist - The open-source, web-based thinking tool that facilitates effective thinking for solving problems.