Here's a great paradox that relates with this topic:
One seemingly ordinary overcasted day a group of people went on a picnic together. Then, from out of the blue an alien ship came down and landed right next to the park where these people were eating. An alien came out of the spaceship and came over to the group of people. He announced to them that he had perfect foresight and he could predict anyone's personal decision with 100% accuracy. Of course everyone doubted him.
So he said he would prove it to them, "I have with me two boxes, under one will always be $1000, but under the other will be either $0 or $1000000. You have a choice, you can either pick both boxes in which case there will be no money under the second box and you will earn only $1000, or you can pick the second box in which case there will be the $1000000 under it. Sense I have perfect foresight I will know what choice you will make beforehand and will either put the money under the second box or won't (hidden from view of course). Then you may go up to the boxes, make your choice, and the appropriate money will be waiting for you."
The first person to go up thought to herself, "Sense the alien has already put the money under the boxes, no matter what choice I make the money is there and its not going anywhere. So if I choose to take what's inside both boxes I will at least end up $1000 richer."
After many people made this same choice (and they all got merely $1000) a man decided to try the other option. "I've seen all of these people go and get the money the alien promised they would get for their choice. I trust this alien does have perfect foresight and so I will choose to take only the money under the second."
The man made his decision and sure enough he got his $1000000.
I'm not making any claims to whether or not this supports/opposes the claim of free will, I just thought it might be something additional to think about during this discussion.