If you have a book or specialized reports and articles you can have them formatted to be sold to millions of Palm Pilot and Visor users. This market is growing by leaps and bounds and there is no reason you can't tap it.
Not only that. Just think of the possibilities when you are at meetings or on airplanes and you run into a hot prospect. Simply beam him/her your book. This sure beats the heck out of a simple business card.