[legutierr]

Are you aware of any such editor that does store the data in Markdown or something similar?

[yesbabyyes]

Take a look at bergie's Hallo editor:

http://bergie.github.com/hallo/markdown.html

He also has an interesting project called Create:

http://createjs.org/

[patrickg]

Not really what you're after, I guess, but a link anyway: http://code.google.com/p/pagedown/wiki/PageDown "PageDown is the JavaScript Markdown previewer used on Stack Overflow and the rest of the Stack Exchange network. It includes a Markdown-to-HTML converter and an in-page Markdown editor with live preview."

[kodablah]

https://github.com/OscarGodson/EpicEditor

[zalew]

http://markitup.jaysalvat.com/home/