It is hard to find a real classic that has not yet been brought up. Certainly my first recommend is Code Complete, which seens to be on everyone's list.
in reply to Which non-Perl books made you a better (?:Perl )?Programmer?
However there are some business books that are particularly enlightening for programmers who want to understand the dynamics of the world they live in. In particular I recommend Information Rules to understand the dynamics that lead to vendor lockin, how standards are set, why customer support sucks, and other realities of the IT world. To help you identify which products and companies are on their way in or out (very important when making career decisions!), I recommend either The Innovator's Dilemma or The Innovator's Solution. The latter is probably more useful than the former since it focuses on how the theory applies in practice while the former tries to convince people of the theory.
Oh, and I highly recommend Winning at New Products. I don't I recommend it specifically to junior programmers in particular, but I definitely recommend it...