Sam Harris has made an excellent albeit a bit short TED talk about science and moral questions:
He naturally got a lot of negative critique for this talk. He is not claiming that science can dictate morals exactly, what he is saying is that there are moral truths to be known. The fact that science has no complete explanation for reality, does not prevent the existence of scientific truths, as does not the lack of a scientific model for morals prevent there from being any moral truths.
Sam Harris has posted a response to the critique here:
Moral confusion in the name of “science”
