In this day and age, I think books are starting to wane in importance, in the world of programming, but there are a lot of classics that are well worth your time.
I think it's also important for programmers to learn a bit about economics, marketing and business in order to better understand the world. I recently created a web site to summarize business books, which contains a lot of my favorites. It's available here: www.squeezedbooks.com.