PDF Cube uses the OpenGL API to add spinning cube page transitions to PDF documents
PDF Cube is an OpenGL API-based PDF viewer that adds a compiz/Keynote-like spinning cube trasition effect to your PDF presentations (including Latex, Beamer and Prosper). You can also zoom on 5 predefined areas of any presentation page with a smooth zooming effect.
That pretty much says it all. It's still pretty alpha-quality, but it might be part of a cool solution to the presentation software dilemma some day. If you're interested, check it out.