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.
Markdown Here - Google Chrome, Firefox, and Thunderbird extension that lets you write email in Markdown and render...
iPython - iPython provides a rich toolkit to help you make the most out of using Python interactively.
Dillinger - joemccann has 95 repositories available. Follow their code on GitHub.
Kajero - Interactive JavaScript notebooks - create good-looking, responsive, interactive documents.
The Most Dangerous Writing Prompts - Don't stop typing, or all progress will be lost.