I've made a realtime one that does not require the user to know html (I got it as close to a word-processor as I could). It uses a lot of complicated Javascript code, though, in order to do much of the work on the user's end. And it isn't documented.
The data is stored compactly as code, and the html is created on-the-fly when the page is viewed.
I've put a lot of time into it (1000+ hours?). But perhaps if I put it up on say SourceForge, it could be improved (and documented).
Here's a screenshot of the text interface.
http://www.bigmweb.com/images/text.gif
So... I'd like to know how much interest there'd be in such a project.
Mike