Trilight Zone

[digital8]

In Japan, the anonymous P2P clients Winny and its successor Share are the most popular filesharing clients in the country.
In the United States, Freenet is a mildly popular P2P network that is used as an anonymous, P2P version of the World Wide Web.
Azureus was the first BitTorrent client that made it possible to switch to anonymous mode on the I2P and Tor (anonymous network).
ANts P2P allows P2P file sharing and HTTP publishing/consulting. The irc chat feature is not anonymous, only the personal peer to peer messages are as well as secure as data transfers.
Entropy was written in response to Freenet. It accomplishes the same task, and has the same interface, but the internal implementation is very different, it's written in C, it claims to be much faster, and easy on the computer's resources.
Free Haven
GNUnet
I2P
IIP Invisible Internet Relay Chat Project
IRIS
JetiAnts
MFC Mute, written in C.
Napshare, written in wxWidgets, is a client of the MUTE and so called KEY network.
Mnet
Mojo nation
MUTE
Nodezilla
Publius
http://www.peercast.org
Rodi
Tangler
WASTE is an anonymous client for a small network of trusted peers, run only by those peers. Works optimally with individual networks of 50 peers at most.