What editor do you currently use? What is "the best"?
[Edit] I do think I'd prefer the editor to generate Markdown that I want to store, but it could generate "clean" HTML/XML/JSON too.
[Edit2] I thought about a Javascript editor to be embedded in a website.
Out-of-the-box, it likely isn't what you want, but if you learn how it and its plugin system works, you can make it what you want.
Their team also is fairly awesome - as we've twisted it to our needs, their support folks have always been there for us to not only answer questions, but even going so far as to understand what we are trying to do, and having their dev staff send us sample code to help us out.
Something that'll render Markdown as you type? There are a few
Something that's more-or-less Dreamweaver...but on the web?
Something like Google Docs?
I do think I'd prefer the editor to generate Markdown that I want to store, but it could generate "clean" HTML/XML/JSON too.