These Japanese are crazy... The last thing they've managed to do is to embed a Actionscript compiler right inside the browser. On top of that the site has basic community features where you can code your own snippets and remix other people's.

http://wonderfl.kayac.com/

Coding on that window is a bit tricky, but it was fun, somehow. I wonder how the project will end up.

I added some of my snippets on my profile:

http://wonderfl.kayac.com/user/mrdoob