Phoenix Labs presents PeerGuardian, an open source IP blocker for Windows and Mac OS X that integrates support for multiple lists, list editing and automatic updates to protect users' privacy on P2P. Includes a wiki, a link to their IRC channel and a FAQ section... 

http://phoenixlabs.org/

Open source, multi-platform, multi-protocol client. Includes support for eDonkey2000, Overnet, BitTorrent, Direct Connect and Fasttrack, and is written in Objective Caml... 

http://mldonkey.sourceforge.net/

Open source program for Windows which has its own network derived from Gnutella and which is also able to handle BitTorrent and Shoutcast... 

http://aresgalaxy.sourceforge.net/

Open source Windows client for the ED2K and de-centralized Kad networks released under GPL... 

http://www.emule-project.net/

A cross-platform, open source Gnutella and BitTorrent client optimized to work behind firewalls and derived from LimeWire's source code... 

http://www.frostwire.com/

Shareware peer-to-peer file sharing program for OS X which connects to Gnutella and BitTorrent networks. Features list, support forum. Mac OS 10.2 or higher... 

http://www.acquisitionx.com/

Offers an open source peer-to-peer client software package compatible with the Gnutella file-sharing network. Also supports BitTorrent and private, secure file sharing with friends... 

http://www.limewire.com/

Free software which lets users 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... 

http://freenetproject.org/

TorrentFreak is a weblog dedicated to bringing the latest news about BitTorrent and everything that is closely related to this popular filesharing protocol... 

http://torrentfreak.com/

BitComet is a BitTorrent/HTTP/FTP download management software, which is powerful, fast, very easy-to-use, and completely free. It contains many advanced features that can accelerate your downloading up to 5 - 10 times faster, or even more... 

http://www.bitcomet.com/