Here's a classic text that no-one has mentioned yet: Computer Power and Human Reason: From Judgement to Calculation by Joseph Weizenbaum. I notice that someone has stolen it from my bookshelf. Hmmm, that's the second time that has happened.

An absolutely crucial read to anyone working in the field of computing (especially when you work with other people who don't).

I'll also second anything written by Jon Bentley, especially Programming Pearls, More Programming Perls, and Efficient Programming.

And to add a contrarian opinion, I was rather underwhelmed by The Pragmatic Programmer. Whether that means I'm pragmatic by nature, I don't know, but I didn't come away from with any new insights.