for (Graduate) Students
All students who are thinking about going to graduate school, or want to go to graduate school, or even who are presently in graduate school should read the following two books.
Getting What You Came For, by Robert L. Peters, is for all students and gives advice and information from "so you want to be a grad student?" to "getting a job" and on. This book is really the handbook for graduate school. Even if you think you know what you are doing, this book will help you be more certain you are right. It's also very affordable (less than $15, currently $11 at Amazon), and most bookstores carry it in stock, so there is no reason not to have a copy.
A Ph.D. Is Not Enough, by Peter J. Feibelman, is primarily geared toward scientists, although, I think much of the advice is generalizable enough to be applicable to many disciplines, not just the sciences and engineering.
Philosophy and Ideas
Here are some readings and writers I highly recommend (and what I'm currently reading):
My adviser's excellent notes on AI Programming (and Lisp).
Philosophy of/on Artificial Intelligence
Daniel Dennett's essay "Why You Can't Make a Computer That Feels Pain" (which can be found in his book "Brainstorms" - an organized collection of his essays) is an excellent Philosophical discussion on the limitations of computers and Artificial Intelligence.
The Discoverers by Daniel J. Boorstin A history of mans greatest discoveries, what made them possible, and what prevented them from happening sooner.
Paul Graham is a venture capitalist who made millions building ViaWeb which was bought out and is now Yahoo Stores. He has a large collection of essays on topics ranging from building a startup, to guidance on engineering and design, and even his theory on "why nerds are unpopular".