Gnunet.org (Visit site )

GNUnet is a free software framework for decentralized, peer-to-peer networking. The framework offers link encryption, peer discovery and resource allocation. The primary codebase is written in C, but with Freeway there is an effort to produce a compatible version written in Java. GNUnet currently runs on Linux, BSD, Mac OS X, Solaris and Windows. It is an official part of the GNU project.