I had a professor in college who was adamant that we do not have free will. His argument basically boiled down to this: we are who we are because of our genes, our environment, and random events that go on in the brain. We can't control any of them. Sure, you may be able to control your environment, but how we choose to do so is influenced by everything in the past. We think the way we do because of events we couldn't control.
Here's an interesting paper he wrote on the subject: http://www.pnas.org/content/107/10/4499.full