Nature's Miracle is one. They changed the formula a few years back and it's not as good at it used to be, but it does work. You have to use it directly on the accident though, so for a new puppy who might 'drip' a bit or hide their 'mistake' for a few hours, it only marginally helps.
We are just waiting until she's trained and then we plan on getting the carpets cleaned professionally (or replaced with hardwoods if we don't need a new roof between now and then

).
I am going to try a bowl of white vinegar in the room to see if that helps at all...