DocBook now has a DTD for producing slides. The DocBook project provides XSL stylesheets for creating slideshow presentations in HTML.
Instead of using HTML for presenting slides, this XSL stylesheet creates an SVG document that presents the slideshow. The idea is to have a slideshow presentation that (at least) mimics MS Powerpoint. In time, we hope to make the stylesheet create SVGs that are rich in features and allow for much flexibility in the presentation, such as non-linear slideshows.