Feeling nostalgic for the almost forgotten written letter, author and former ad man Ivan Cash fell upon a simple idea: he invited anyone in the world to send him an email, and he'd write it out in a letter and mail it, for free. Participants could even request a doodle or to seal it with a kiss. What started out as a personal art project exploded into a worldwide event. As requests poured in, Cash enlisted an international army of volunteers who helped...