The famous example of a philosopher changing his mind is Frank Jackson with his Mary's Room argument. However, that's pretty much the exception which proves the rule.
Jackson is the first example I thought of. As I understand it, he came to be convinced, particularly by the arguments of David Lewis, that rejecting physicalism made it harder, rather than easier, to explain what was going on. But calling it "the exception that proves the rule" seems lazy and unhelpful, especially in light of other examples people have mentioned here.
Sam Harris is here offering a substantial amount of money to anyone who can show a flaw in the philosophy of 'The Moral Landscape' in 1000 word or less, or at least the best attempt.
http://www.samharris.org/blog/item/the-moral-landscape-challenge1
Up to $20,000 is on offer, although that's only if you change his mind. Whilst we know that this is very difficult, note how few people offer large sums of money for the privelage of being disproven.
In case anyone does win, I will remind you that this site is created and maintained by people who work at MIRI and CFAR, which rely on outside donations, and with whom I am not affiliated.
Note: Is this misplaced in Discussion? I imagine that it could be easily overlooked in an open thread by the sorts of people who would be able to use this information well?