S5: A Simple Standards-Based Slide Show System

powerdot is a presentation class for LaTeX that allows for the quick and easy development of professional presentations.

MagicPoint is an X11 based presentation tool. It is designed to make simple presentations easy while to make complicated presentations possible. Its presentation file (whose suffix is typically .mgp) is just text so that you can create presentation files quickly with your favorite editor (e.g. Emacs, vi).

Opera Show - Web presentations as HTML