1. Codeply

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

  2. CodePen

    A front end web development playground.

  3. JSFiddle

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

  4. Plunker

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

  5. JS Bin

    Sample of the bin:

  6. Pastebin.com

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

  7. kodeWeave

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

  8. Liveweave

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

  9. Dabblet

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

  10. CSSDeck

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

  11. CSSDesk

    CSSDesk is a online HTML/CSS sandbox.

  12. Clippr.co

    Minimal Note Writing And Pasting Site