I like this posting by Seth Godin.
A presentation is a precious opportunity. It's a powerful arrangement... one speaker, an attentive audience, all in their seats, all paying attention (at least at first). Don't waste it.
The purpose of a presentation is to change minds. That's the only reason I can think of to spend the time and resources. If your goal isn't to change minds, perhaps you should consider a different approach.
1. The best presentation is no presentation at all. If you can get by with a memo, send a memo. I can read it faster than you can present it and we'll both enjoy it more.
2. The second best presentation is one on one. No slides, no microphone. You look me in the eye and change my mind.
3. Third best? Live and fully interactive.
4. Powerpoint or Keynote, but with no bullets, just emotional pictures and stories.
5. And last best... well, if you really think you can change my mind by using tons of bullets and a droning presentation, I'm skeptical.
A presentation isn't an obligation, it's a privilege.