CodePen - A front end web development playground.
Coding View - Coding View is live collaborative coding environmentdesigned for technical phone interviews. It features web version of Visual Studio Code, as well as access to real terminal. It has a built-in compiler for most popular programming languages.
JSFiddle - Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor.
codebunk - Realtime Collaborative Editor with Code Execution, REPLs and Chat
JS Bin - Sample of the bin:
Google Classroom - Learning management tool by Google