I strongly recommend the 10-20-30 rule set out by Guy Kawasaki at http://blog.guykawasaki.com/ In short, 10 slides, 20 minute-Talk, all fonts on slides at least size 30 or more. It's not as easy to follow this as you might think, but it certainly forces you to cut the fat off your presentation.Give it a try and send your evaluation to the open forum for others to learn from your experience.

Here's what Guy Kawasaki had to say:

I am trying to evangelize the 10/20/30 Rule of PowerPoint. It’s quite simple: a PowerPoint presentation should have ten slides, last no more than twenty minutes, and contain no font smaller than thirty points. While I’m in the venture capital business, this rule is applicable for any presentation to reach agreement: for example, raising capital, making a sale, forming a partnership, etc.
Ten is the optimal number of slides in a PowerPoint presentation because a normal human being cannot comprehend more than ten concepts in a meeting—and venture capitalists are very normal. (The only difference between you and venture capitalist is that he is getting paid to gamble with someone else’s money). If you must use more than ten slides to explain your business, you probably don’t have a business. The ten topics that a venture capitalist cares about are:
1. Problem
2. Your solution
3. Business model
4. Underlying magic/technology
5. Marketing and sales
6. Competition
7. Team
8. Projections and milestones
9. Status and timeline
10. Summary and call to action

Cheers,

Steve