http://gizmodo.com/5927379/the-secret-o ... e-anything
You need to know how to use Tor to get on it. Basically it's an arms bazaar.
You know me, I'm a freedom nut, but I happen to believe that deadly weapons need a certain amount of control ascribed to their purchase. Basically I think the final acquisition needs to be done person-to-person.
You can actually buy weapons online via normal websites, but they get shipped from the dealer, to a dealer close to you, where you do the final paperwork and acquire your piece.
This site basically ships 'em to you in pieces and you have to put it all together. Interesting proof of concept, but a little off-putting. Not everyone is a responsible citizen.