If you are reading this is because you want not only want to make better presentations, but because you also want to make them faster. So my question to you is, do you know your tools? Whether you use PowerPoint or Keynote, you should know how to use them…efficiently. Practice is not enough, you might have create hundreds of presentation stacks without improving your knowledge of the tools you use. You need to understand the User's Guide and learn the most important Keyboard Shortcuts.
Here is my post on 20+ very useful Keynote Shortcuts. PowerPoint Ninja has a post on Essential PowerPoint Shortcuts. If you want a challenge here you have all PowerPoint 2010 and Keynote'09 shortcuts. Go and practice.