Plunker is another "jsfiddle" competitor.
Why you should try it?
- it's editor has a cool elegant design
- is uses - ACE/Cloud9 as its code editor (based on mozilla's bespin open source project).
- its uses twitter's bootstrap for css.
- it has built-in boilerplates for starting your own "plunker" such as - backbone, angular, bootstrap etc.
- it has a live preview pane which shows the review of the code
- it also has a nice restful api for developers