McConnell, S. Code Complete . Redmond, WA: Microsoft Press, 1993. Software developers are paid to produce code and other stuff. Plenty of stuff has been written about the other stuff, much of which is fluff. This is the best book ever written on code. I remain hopeful that Steve updates the book to include modern techniques.
Fowler, M. Refactoring: Improving the Design of Existing Code . Reading, MA: Addison-Wesley, 1999. Martin's book contains a wealth of practical advice on how to engage in refactoring throughout a system.
Schneier, B. Applied Cryptography: Protocols, Algorithms, and Source Code in C, 2nd Edition . New York: John Wiley & Sons, 1995. Although somewhat dated, Schneier's book provides developers with a detailed understanding of many of the lowest set of protocols and standards that form the foundation of many security approaches.