The perhaps most widely used darknet software is Nullsoft's WASTE. The developers of Freenet have stated that they are working on a new version that will be a darknet, which unlike typical Darknets, will be capable of supporting potentially millions of users using an application of small world theory.

WASTE behaves similarly to a virtual private network by connecting to a group of trusted computers, as determined by the users, however this kind of network is commonly referred to as a darknet. It employs heavy encryption to ensure that third parties cannot decipher the messages being transferred. The same encryption is used to transmit and receive instant messages, chat, and files, maintain the connection, and browse and search. There is also an optional "Saturate" feature which adds random traffic, making traffic analysis more difficult. The nodes (each a trusted connection) automatically determine the lowest latency route for traffic and, in doing so, load balance. This also improves privacy, because packets often take different routes.

http://sourceforge.net/project/showfiles.php?group_id=82356&package_id=84413&release_id=302514

go justin!