In the order in which I thought of them:
Gödel, Escher, Bach: an Eternal Golden Braid, Douglas Hofstadter. A treatise on the nature of music, mathematics, art, and the mind. Full of mind puzzles, puns, and incredible cleverness. This book has consistently delighted me since I was 14.
The Art of Happiness, Tenzin Gyatso, 14th Dalai Lama, and Howard C. Cutler. The book that reminds me that my mission in life is to be happy, and that a good way to accomplish that mission is to approach it like a scientist.
Thief of Time, Terry Pratchett. This book reminds me that however long or short my life is, I can make it seem longer or shorter by the way I pay attention to it. Interestingly enough, this is the only work of fiction on my list.
Improv Wisdom: Don't Prepare, Just Show Up, Patricia Ryan Madson. This is a book for those times when I don't want to approach my mission in life like a scientist. It reminds me that I should also approach it like it's a game.
The Patient who Cured his Therapist, Stanley Siegel. Siegel's wonderful thesis is that the very things that we think are our psychological problems are actually adaptive behaviors that help us be happier and more fulfilled, and that by understanding and respecting them we can turn them to our advantage.
The Brain that Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science, Norman Doidge. Full of tantalizing recent evidence about the remarkable plasticity of the human brain, with hints about what we can do to make ourselves smarter day by day.
How to Win Friends and Influence People, Dale Carnegie. A tolerably machiavellian guide to building trust and friendships. As a youngster, I was your typical clueless and socially maladjusted nerd. This book was one of my first steps toward finding more meaningful relationships with the people around me.
Summerhill: A Radical Approach to Child Rearing, A. S. Neill. A possibly crazy visionary talks about the revolutionary school he built in Britain, where students are raised to be independent thinkers, to a degree that is inspiring and hard to believe.
In the Beginning...was the Command Line, Neal Stephenson. A love letter to computers, and to the way they all used to be used, by typing commands. A beautiful reminder of how the written word retains its power even when the reader is a computer rather than an intelligent being.
The Adventures of Johnny Bunko: The Last Career Guide You'll Ever Need, Daniel H. Pink. Short, sweet, fun, and to the point. Career advice I wish I'd been given when I was 20.
Illusions: The Adventures of a Reluctant Messiah, Richard Bach. A nice elaboration of one of the few possible types of metaphysics that my agnostic mind is willing to consider.
The Art of Electronics, Paul Horowitz and Winfield Hill. Electronics is in many ways more of an art than a science, the kind of thing one expects to only be able to learn from experience and trial-and-error, something unteachable. Yet this book teaches it.
Tuesdays with Morrie: An Old Man, a Young Man, and Life's Greatest Lesson, Mitch Albom. This book has served as one of the best reminders to me to live my life to the fullest, and to love all the incredible people surrounding me.
Apple Inside Macintosh, Volumes I, II, and III, Caroline Rose and Bradley Hacker. These three volumes, the canonical documentation for the Macintosh computer back when the best you could get was a Mac Plus, are in my opinion the gold standard of technical documentation. I am especially enamored with the chapter on Quickdraw, the early Macintosh's graphics library, and the careful design that clearly went into it.
QED: The Strange Theory of Light and Matter, Richard Feynman. I don't know what it's like to read this book if you don't have a B.S. in physics. But if you do, it bundles up all the physics you've ever learned, plus some you didn't know, and hands it to you in a neat little package. In effect, Feynman says, "These are the dice God uses when he plays his little universe game, and here is how he loads them."
The Evolution of Cooperation, Robert Axelrod. An intriguing analysis of how a species of mutually cooperative creatures could have evolved from a previous species that did not cooperate. Based on fairly simple computer models, but with useful lessons about how to foster cooperation in the real world.
Writing Solid Code: Microsoft's Techniques for Developing Bug-Free C Programs, Steve Maguire. One of the best books I've ever seen about how to be a truly professional programmer. Ignore the tagline. This book is free of Microsoft bullshit and it's applicable to far more than just C programs.
Drawing on the Right Side of the Brain, Betty Edwards. I never learned to draw from this book, but it provided a great deal of guidance into introspecting about what is going on in my mind when I'm improvising music on the piano.
Zen and the Art of Motorcycle Maintenance, Robert Pirsig. This book was a thrilling read back when I was in college. I'm not sure what it would be like to read again now that I've mellowed out a bit, but it was such a delight back then that it deserves a place in this list.
The Language Instinct, Steven Pinker. I read this book at a time when I was in a bit of a linguistic rut, and it reminded me of how much I love language. I credit this book, or rather the mental attitudes it helped me develop, with my rapid acquisition of Spanish during my trip to Mexico in January.