If I had the skill I would do this myself, but can someone with web saavy come up with a clickable map of the US where each of us could click on the state we live in and get a running count of cars in the state? Tomorrow the world!
There are already websites where you can do this, but I don't remember them off the top of my head.
Found one for the roadster, but haven't seen anything for the Model S.
World Map of Model S Reservation Holders maintained by one of the moderators over at Tesla Motor Club:
That map is voluntary listings only, a small percentage of the real numbers.