This really stinks.
Why is he making you wait two weeks? Obviously they erred in sending the package to the wrong address, the fact that you USED to live there is barely relevant (it's a good excuse for the mess-up, but hardly grounds to accuse YOU of any wrongdoing!)
If the vendor is in the same state as you are, then small claims court is probably your best route if nothing materializes in two weeks. If he's out of state, I have no idea how the rules apply, but I'm guessing that it's not as easy to file a suit unless you're willing to travel to the city in which the vendor does business (I did a *little* bit of checking in to this during my dispute with my LDS).
As other people have mentioned, whenever possible, conduct transactions like this with a credit card - they'll help you out in cases like these. I don't know if the USPS could help at all since you used their service to pay for something that didn't arrive - I wouldn't be surprised if they can, but that's pure speculation on my part.
Good luck, sig, I hope this all works out for you.