Re: xhtml+MathML as a format for slides

 > At least a few of us know that W3C's "slidy" package for HTML
 > slides is compatible with XHTML+MathML.

Along those lines, Instiki

    http://golem.ph.utexas.edu/wiki/instiki/show/HomePage

has built-in support for slideshows,

    http://golem.ph.utexas.edu/wiki/instiki/show/S5

based on S5. But, unlike Slidy, which would require the user to author  
well-formed XHTML+MathML, the input format for Instiki is much more  
user-friendly. While you *can* enter raw XHTML(+ MathML), it's much  
easier to author your slides using Markdown

    http://maruku.rubyforge.org/maruku.html

plus itex.

    http://golem.ph.utexas.edu/~distler/blog/itex2MMLcommands.html

Cheers,
Jacques