replit - Code, create, andlearn together. Use our free, collaborative, in-browser IDE to code in 50+ languages — without spending a second on setup.
Pastebin.com - Pastebin.com is a website where you can store text for a certain period of time.
JSFiddle - Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor.
GitHub Gist - Gist is a simple way to share snippets and pastes with others.
CodePen - A front end web development playground.
Write.as - Publish a thought in seconds