Jockeystreet lists the 72 books that he considers to be the most influential to him. Among his authors are Noam Chomsky, Jack Keroauc, Saul Alinsky, Peter Singer, and Soren Kierkegaard. I think that this is a simply fascinating exercise. I would provide my own list, but I think that it's largely redundant after these posts.
What books have been the most influential to your thinking?
UPDATE: Blogger links are acting up again, so you may have to edit the links in your URL bar.
UPDATE x2: Okay, the links appear to work now.