1. Responsive Design Playground & Frontend Editor. Use, compare & test responsive frameworks. Find code snippets & examples.

  2. Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor.

  3. Plunker is an online community for creating, collaborating on and sharing your web development ideas.

  4. Pastebin.com is a website where you can store text for a certain period of time.

  5. HTML/CSS/JS and Markdown Code Playground For Web Designers and Developers

  6. dabblet is an interactive playground for quickly testing snippets of CSS and HTML code.

  7. Collection of Awesome CSS and JS Creations to help out frontend developers and designers.

  8. Online Interpreters in JavaScript. Online coding and REPL. Run and share code.

  9. Liveweave is a HTML5, CSS3 & JavaScript playground for web designers and developers