Well you can look at NARTH's website for starters. Then there's a video the AFA is ciculating called "It's Not Gay."
Personally, I don't know if they are 100% effective, as they claim, but I would think that any person has the ability to alter their behavior even if they cannot wholly eliminate a desire. Just like a hot-tempered person (such as myself)doesn't angrily lash out everytime they feel they are justified, a homosexual (or heterosexual for that matter) doesn't have to act on every sexual impulse.