Woah: Silk Road is an Internet narcotics market. Visit the market via Tor, pay in Bitcoins, and receive your LSD by mail! The Silk Road web site only exists as a Tor hidden service, but you can sometimes see it (non-anonymously) via this proxy. On the public Internet, here's the founders' feedback thread on Bitcoin's forums.

I'm fascinated by how it works. I'm going to quote their "About" page in full, because I'm guessing it won't be online much longer.

Silk Road is an anonymous marketplace where you can buy and sell without revealing who you are. We protect your identity through every step of the process, from connecting to this site, to purchasing your items, to finally receiving them.

Connecting to the site: Silk Road uses the Tor network to anonymize all traffic to and from the site so no one can find out who we are or who you are from your internet traffic. All traffic is encrypted and relayed through Tor nodes accross the globe, each one not knowing the origin or destination of the traffic. To learn more about the Tor network, visit torproject.org.

Purchasing your items: The currency used to buy stuff on Silk Road is called Bitcoin. Bitcoin uses encryption and a system of peer-to-peer double checking to create a completely digital currency. No personal information is associated with your bitcoins at all, making them ideal for anonymous transactions. Additionally, Silk Road employs a built-in tumbler that mixes all incoming bitcoins through a series of dummy transactions before they ever leave. Click here for instructions on how to get Bitcoins, or visit Bitcoin.org to learn more.

Delivery: Absolutely none of your personal information is ever required here. However, an address WILL be needed to accept delivery of any physical goods. Even so, it is stored encrypted, and is deleted as soon as your transaction is complete, so there is no record of it. And, because Silk Road is a Tor Hidden Service, the address remains encrypted within the Tor network when it is transfered.

For more details about improving your anonymity and making purchases, please read our buyers guide.

I'm particularly struck by their statement they provide a BitCoin laundering service. I'd noticed BitCoins didn't seem particularly anonymous, here's proof that someone with a vested interest in real payment anonymity agrees.