This is a collection of "must haves" for the scholarly hacker. Each one is generally considered a definitive (or canonical) reference for its particular topic. In the absence of a book listed here, O'Reilly and Associates generally do a good job of covering any topic they set their mind to.
And, I can't really let you buy books without stating that I disagree with Amazon.com's recent patents. They seem to be patenting really obvious ideas, using the naivité of the USPTO and the courts (as far as technology) to give them an unfair advantage over their competitors. I will soon be putting up alternative links to allow you to buy these books from other bookstores (thus depriving myself of the income, but satisfying my sense of fairness). In the meantime, try Readme.Doc or FatBrain.com.
Books on programming languages