Powerpoint on the Web without Paying Microsoft?
If you're comfortable hand-coding html or using a tool that can be massaged to take the stylesheet of your choice, there's a completely XHTML/CSS solution.
The reflexive demonstrations is here: http://www.w3.org/Talks/Tools/Slidy
A nice primer is here: http://meyerweb.com/eric/tools/s5/primer.html
--E. R. O'Neill