> Just an idea: what do you think of TeX?
> Gives print and (with latex2html) HTML.
> 
> As an alternative, I've made good experiences with
> http://www.feyrer.de/Texts/Own/NWF/nwf_toc.html.
> 
> No, it's not XML, but so what.

I have used latex2html a lot.

I heard it is unmaintained.

Another tool is TeX4ht
http://www.cse.ohio-state.edu/~gurari/TeX4ht

and tth:
http://hutchinson.belmont.ma.us/tth/

And hevea:
http://pauillac.inria.fr/~maranget/hevea/index.html

Last I heard XML to print usually use latex.

I think staying with XML is fine for our website. I have no advice either 
way.

I do use latex a lot especially with LyX for letters, course books, other 
books, etc.