I'm a marathon runner, with 60 races done all over the world, halfway home to my ultimate goal of 100. I use the iPod Shuffle as a perfect training-aide. It makes the repetitious (running long miles and gym sessions) rhythmic, inspirational and entertaining. It shrinks time. An hour on an Elliptical-machine at the gym feels ten minutes long when 150 of my favorite tunes are rocking-and-rolling me along. (Favorite song? Eminem's anthem to timing and excellence: "Lose Yourself" -- perfect way to get jacked-up pre-workout or pre-performance at a marathon starting line). -- Michael Modzelewski