[theduality]

For a general software developer, I have seen Code Complete (Steve McConnell) and Clean Code (Robert C. Martin) recommended a lot. I have copies of both on my desk at work.

[coldtea]

Design Patterns (GoF), The Mythical Man-Month,

[majewsky]

I'm skeptical about the GoF book. To often, it's been the proverbial hammer that makes you see nails everywhere.

[lkbm]

The Pragmatic Programmer (Andy Hunt and Dave Thomas) is the other one that springs to mind for me.

[LandR]

I'd add SICP.