Rands in Repose on not needing slides to convey your message during a presentation:

It’s you up there on stage. They paid to see you. If they simply wanted to know what you think, they could have read your weblog or bought your book, but they paid to see you. A presentation is not just the careful construction of your thoughts; it’s a means by which your audience has access to you — pacing, waving your arms, and cleverly recovering from that disaster on slide #32.