I think the question of what (if any) is the role of philosophy in light of modern science and atheism is an extremely interesting one. I studied philosophy at two major US schools and its amazing as I think back how many questions are resolved once you accept atheism and a scientific outlook.

I think that a lot of philosophy has been just another branch of pseudoscience, with no more validity than religion, astrology, or creationism. Postmoernism is the most obvious bad example. However, I think there will still be a legitimate need for philosophy for quite some time. I think the best definition of philosophy that I've heard was made by Sam Harris. I forget his exact words but he said something like philosophy is what we do when our knowledge is too immature to be science.

I think a good example of a field that is currently so immature it needs philosophy (and one I'm sure Harris had in mind) is human ethics. We may as Harris believes one day know enough about human neurophysiology to use it for a complete explanation of human ethics. However, we are a long way from that and in the mean time its worthwhile to apply rigorous thinking to ethical questions.