The Triathlete's Training Bible by Joe Friel - One of the greatest training books I have ever come across. I used the principles in this book to train for my first Ironman (check me out) and the results were amazing. From training schedules to workouts to eating - absolutely everything is covered.
	In Fitness and in Health by Dr. Philip Maffetone - This book describes Phil Maffetone's training philosophies regarding diet, exercise, and heart-rate based training. He advocates building fitness by keeping your aerobic system healthy. This book discusses diet much more than training, but is perfect for the athlete that wants to eat healthier for fitness and performance.
	The Maffetone Method : The Holistic, Low-Stress, No-Pain Way to Exceptional Fitness by Dr. Philip Maffetone - To illustrate how his program works, Maffetone profiles four common types of individuals: someone who works out but whose program needs modification; someone who stops and starts exercising on a regular basis; a true beginner; and someone who needs to begin an exercise program because of poor health.
	Swim, Bike, Run by Glenn Town, Todd Kearney - The best book I have found for an overall view of Triathlon training. Covers everything you need to know about gear, training, racing, eating, and mental preparation. Includes practical training programs for all distances and some great in-depth descriptions of proper form in the three components of a tri.
	Total Immersion: The Revolutionary Way to Swim Better, Faster, and Easier by Terry Laughlin - Learn to swim like a fish. While I'm still no fish, this book has helped my swimming technique immensely. It provides step-by-step drills and lots of great theory, including tips and tricks for open water swimming.
	Total Triathlon Almanac by Tony Svensson - A comprehensive logbook/diary for triathlon training. Includes techniques for planning a training program and tips from many of today's successful triathletes. A must for the bookshelf - you will use it daily.
	The Inner Game of Tennis by W. Timothy Gallwey - Written about Tennis but applicable to just about anything. Gallwey uses tennis as the medium through which he explores the "Inner Game" or the ability to overcome self-doubt and lapses in concentration. I reread this book at least once a year.