I made my own open source coding playground called kodeWeave (which saves and retrieves your weaves as a Github Gist). It's available for Windows, Linux, Mac OS X, Android and Online (I also plan on releasing it for iOS and Windows Phone too).

Some other good coding playgrounds to tryout are CodePen, CSSDeck, Plunker, JSBin, jsFiddle, Liveweave.
There is also Brackets which is an open source project created by Adobe (It's basically the open source version of Edge Code). The nice thing about Brackets is it runs off it's own server locally on your device so if you're using a library like JSZip it works right away. In addition whenever you save a change made in a file in Brackets your app will reload in Chrome's Debugger (launched from Brackets) So debugging is very fast and easy, not to mention there's lots of plugins that are made to increase productivity. It's really tremendous!

There's also the Cloud9IDE.

I'm sure you already know this but the Chrome Developer Tools has this capability as well.