Kvasir is a project mainly written in JavaScript, it's free.
made of spit, killed by dwarves. Also - HTML5 / CSS / JS presentations
HTML 5 presentations.
To get a PDF version, use the wkhtmltopdf available from: http://code.google.com/p/wkhtmltopdf/
I use the following command-line:
wkhtmltopdf -s Letter -B 0mm -L 0mm -R 0mm -T 0mm --print-media-type -O landscape http://example.com/path/to/slides slides.pdf