I personally haven't tried any, but I had a nurse tell me that Mederma works pretty well. She recommended it to a lot of her patients that had just had c-sections.
A family friend told me that she used Strivectin to reduce the appearance of the scars from her breast reconstruction. I don't think you can ever get rid of a scar like that, but she said it helped to make it less obvious. What kind of scar are you trying to heal?