Remember the woman whose coworker was constantly staring at her chest? Here's her update.
I took the direct approach. I went to his office, closed the door, and said, "I really don't know how to bring this up, but because I think you're someone who would rather have someone be honest and forthcoming, here it is: I've gotten the impression during our conversations that you seem to be somewhat distracted by my chest. I believe you don't mean to be offensive, and I certainly am not accusing you of sexual harassment, but I wanted you to be aware of my impression for the future."
He took it surprisingly well; he was obviously a bit embarrassed but as I suspected, he didn't really seem to know he was doing it. I talked to him later in the week and he actually seemed to be making a concerted effort to look me in the eye! Since then, he's been more aware of his eye contact issues and we've had no problems at all!