I wanted to throw out a couple books that I've found very helpful in preparing for a presentation as well as preparing slides.
The Presentation Survival Skills Guide
This covers a lot of topics from designing slides or other visual aids to where to stand during the presentation. The chapters are like mini courses about a particular topic on presenting. One thing that I took away from the book was how important a good closure is to a presentation. They compare it to the dismount during a gymnastics competitions, like the uneven bars. How many of those competitions are won or lost in the dismount? How many presentations are lost more often than won because of a rushed or incomplete closure?
Non-Designer's Design Book
We're not professional graphic artists. Well, at least most of us aren't. Still we're expected to generate professional looking slides. With the widespread use of software like PowerPoint more and more professionals are building their own slides without formal training in graphic arts or visual communication. This book won't make you a professional designer, but it will give you some of the fundamental skills to use when building your slides.
One way to think about this is that you can know everything about Microsoft Word and still not be a great novelist. There are other things you need to understand like grammar and character development to be a skilled writer. In the same way, knowing everything about PowerPoint isn't going to make your slides great. This book is like the grammar of visual communication.
I will take Mark to task on his claim of not getting formal training in giving presentations with practice. While less than 1% of Americans have gone through it, I believe that the American military does a pretty good job of providing some formal training in giving presentations with practice. Sure, I've attended some really poor presentations by members of the military and veterans. It wasn't that their training was flawed, but that they were not applying their training to their current presentations. It was because of these courses, and a curiosity about what made one person's slides more interesting and compelling than another's, that led me to the two books listed above.