He rejects naturalistic evolution (the only kind we have any evidence for) and believes instead that his god intervened in the evolution of life on earth. He's even criticized the revamped creationism - "intelligent design" - but only in the way that he thinks IDers are making the mistake of taking a "god of the gaps" approach, claiming god is responsible for everything unexplained. He says that only when he determines a problem is "unsolvable" should it be attributed to his god
This Slate interview from 2009 contains a lot of info.
This is the area where Collins' religion is most in danger of intruding on his science. He believes that it's possible to see evidence of the divine in things like physics equations or patterns of human behavior. While Collins would never suggest that science could furnish any final proof for the existence of God, he's fond of mentioning that the Bible occasionally uses the word evidence. That is to say, he thinks the presence of the divine can be directly observed, even if it cannot be measured and tested.
This is an audacious claim for any scientist to make, and Collins does not deserve a free pass on this from the scientific community.