Well done Dave ... I've been thinking about such a renderer since admiring the output of Marc Barrots OPML renderer ...
Dave asked for examples of CSS rendering of a set of presentation slides ... well how about Tim Berners Lee's recent WWW2002 slides
Seems like a pretty clean CSS encoding with multiple substitutable stylesheets and it even builds 'link rel' structures so that Mozilla and other likewise equipped browsers will build you a nice menu bar to drive the presentation. This is a must if you are going to drive PPT files out of the web for simple presentations (IMHO) ;-)