jsFiddle!

Pastebin.com is a website where you can store text for a certain period of time. The website is mainly used by programmers to store pieces of sources code or configuration information, but anyone is more than welcome to paste any type of text. The idea behind the site is to make it more convenient for people to share large amounts of text online. Users have the ability to make private pastings, so they are only visible to the people they choose to share their links with.

Online playground for testing and sharing HTML, CSS and JavaScript code snippets. Enter your code in the three appropriate panes and see live how it all comes together. You can easily share and fork your own or others creations.

JS Bin is a collaborative open source JavaScript debugging tool. Enter Javascript in one pane and HTML in the other and see the result; share using a short URL. Choose popular JS libs from a menu, so you don't have to remember the URL.

ideone.com is a... pastebin. But a pastebin like no other on the Internet. More accurate expression would be "online mini IDE and debugging tool".

Online Interpreters in JavaScript. Online coding and REPL. Run and share code. Try QBasic, Forth, Ruby, Python, Lua, Scheme, Emoticon, Brainfuck, LOLCODE, Unlambda, Bloop, JavaScript, Javascript.next, Move, Kaffeine, CoffeeScript, Roy programming languages.

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

kodeWeave is a realtime coding playground for HTML, CSS and Javascript. Similar to JSFiddle and JSBin, but kodeWeave was made to work offline but also as a prototyping application to build applications for desktop operating systems while on mobile devices. (PhoneGap Build is recommended for mobile devices)

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

Publish HTML quickly with open source web editor, HTMLhouse. Use the editor / real-time preview to build your HTML page, and press publish when you're done. That's it! No sign up, no fuss.

dabblet is an interactive playground for quickly testing snippets of CSS and HTML code. It uses -prefix-free, so that you won't have to add any prefixes in your CSS code. You can save your work in Github gists, embed it in other websites and share it with others.

Compile and Execute your favorite programming languages online, click any of the following to proceed! Web Technologies, Text Formatting, Useful Utilities, Programming Languages. Vim, emacs modes are avaliable.

CSSDesk is a online HTML/CSS sandbox. Experiment with CSS, see the results live, and share your code with others.

Webmaker - teach your self to code for the web.

Its about quite a few things. You can use CSSDeck to make testcases and share with other people on IRC, forums, StackOverflow, etc. who help you solve your coding problems. You can even code with multiple people in realtime in various modes. Remember etherpad ? Yeah we've got something like that for HTML/CSS/JS coding with lots of other bells and whistles.

Codenvy let's developers contribute to a project in seconds without installing software. Modify, run and debug code in the cloud or on-prem with no software to install.