Robert Cialdini is the president of Influence At Work and the author of, Influence, the Psychology of Persuasion. Along with being one of the nicest people I've ever interviewed he is also the expert on persuasion.
As a Professor of Psychology at Arizona State University he has spent years researching persuasion in the real world. If you're in sales or marketing you can't afford to pass up this show. Listen to Dr. Cialdini talk about the six major forms of influence and how they apply to every day situations.
Influence: the Psychology of Persuasion