Onion Routing Anonymous Network

Onion routing is a technique for anonymous communication over a computer network. Messages are repeatedly encrypted and then sent through several network nodes called onion routers. Each onion router removes a layer of encryption to uncover routing instructions, and sends the message to the next router where this is repeated.
This prevents these intermediary nodes from knowing the origin, destination, and contents of the message.

Onion routing was developed by David Goldschlag, Michael Reed, and Paul Syverson, Tor is the predominant technology that employs onion routing.

Wikileaks

Wikileaks is a website that publishes anonymous submissions and leaks of sensitive governmental, corporate or religious documents, while taking measures to preserve the anonymity and untraceability of its contributors. It's purely based on Onion router technique.