It's remarkable how much you can learn from other programmers. Not by reading their code, mind you, but by realizing that programmers are human beings. Nowhere is that more evident than these two collections of interviews with notable programmers:

Both Programmers At Work: Interviews with 19 Programmers Who Shaped the Computer Industry and Out of Their Minds: The Lives and Discoveries of 15 Great Computer Scientists are packed with amazing insights, even though these interviews are now more than 15 years old.

For more of the human side of software development, I also recommend this list of real world programming stories.