Tor: An anonymous Internet communication system

P2P and anonymity: GNUnet

GNUnet is a framework for secure peer-to-peer networking. The primary application implemented within the GNUnet framework is anonymous censorship-resistant file-sharing.
The goal of the GNUnet project is to provide an infrastructure for secure peer-to-peer networking. All communication in GNUnet is authenticated and link-to-link encrypted. The economic model makes attacks on the network harder since the economics can be used to control resource usage. GNUnet peers exchange messages using a pluggable transport service abstraction. Currently, transport services based on UDP, TCP, HTTP and SMTP are available. The GNUnet core provides mechanisms to perform resource allocations for CPU, bandwidth and storage space. The core enforces resource limitations set by the user. GNUnet does not rely on any centralized services. New Peer-to-Peer protocols can be easily implemented on top of the basic GNUnet infrastructure. Current protocols include anonymous file sharing, a trivial chat protocol, message throughput benchmarking and network topology visualization.

P2P and anonymity: MUTE

 Mute is a file sharing network that uses virtual addresses (instead of IP addresses) and ant-inspired routing algorithms to protect the privacy of both downloaders and uploaders.

• MUTE protects your privacy by avoiding direct connections with your sharing partners in the network. Most other file sharing programs use direct connections to download or upload, making your identity available to spies from the RIAA and other unscrupulous organizations.
• Ants display collectively intelligent behavior when foraging for food or fighting off predators. Each ant in the colony acts in a rather simple way, but together they end up doing something clever, like discovering the shortest path between their ant hill and a food source. MUTE's routing mechanism is inspired by ant behavior.

Here is a lit of available NODES, a collaborative Wiki is also available Mute Wiki

P2P and anonymity: Freenet

 Freenet is free software which lets you publish and obtain information on the Internet without fear of censorship. To achieve this freedom, the network is entirely decentralized and publishers and consumers of information are anonymous. Without anonymity there can never be true freedom of speech, and without decentralization the network will be vulnerable to attack.
Communications by Freenet nodes are encrypted and are "routed-through" other nodes to make it extremely difficult to determine who is requesting the information and what its content is.
Users contribute to the network by giving bandwidth and a portion of their hard drive (called the "data store") for storing files. Unlike other peer-to-peer file sharing networks, Freenet does not let the user control what is stored in the data store. Instead, files are kept or deleted depending on how popular they are, with the least popular being discarded to make way for newer or more popular content. Files in the data store are encrypted to reduce the likelihood of prosecution by persons wishing to censor Freenet content.