GNU/Linux P2P Applications

BitTorrent

Azureus (http://azureus.sourceforge.net/) Proprietary-dependant (Sun's Java Interpreter - Can also be run through GNU Java Interpreter, which is not proprietary)
Hydranode (http://hydranode.com/)
KTorrent (http://ktorrent.pwsp.net/)
BitTorrent (http://www.bittorrent.com/)
GNOME BitTorrent (http://gnome-bt.sourceforge.net/)
MLDonkey (http://mldonkey.org/)
TorrentFlux (http://www.torrentflux.com/)
Extended BitTorrent (http://xbtt.sourceforge.net/)
ctorrent (http://ctorrent.sourceforge.net/)
BitTornado (http://www.bittornado.com/)
BT Queue (http://btqueue.sourceforge.net/)
JTorrent (http://jtorrent.sourceforge.net/)
BT++ (http://btplusplus.sourceforge.net/)
QTorrent (http://thegraveyard.org/qtorrent.php)
Snark (http://www.klomp.org/snark/)
Rufus (http://rufus.sourceforge.net/downloads.php)
rTorrent (http://libtorrent.rakshasa.no/)
Effusion (http://www.azrael-uk.f2s.com/az/effusion/)
Yet ABC (http://pingpong-abc.sourceforge.net/index.php)
Transmission (http://transmission.m0k.org/)
Sancho (http://sancho-gui.sourceforge.net/)

DHT-Based BitTorrent

DHT stands for Distributed Hash Table - a form of decentralization.

Azureus (http://azureus.sourceforge.net/) Proprietary-dependant (Sun's Java Interpreter - Can also be run through GNU Java Interpreter, which is not proprietary)
BitTorrent (http://www.bittorrent.com/)

FAST TCP

FAST TCP (http://netlab.caltech.edu/FAST/index.html) Licensing unknown

eDonkey2000/Kademlia/Overnet

aMule (http://www.amule.org/)
eDonkey (http://www.edonkey2000.com/)
MLDonkey (http://mldonkey.org/)
Hydranode (http://hydranode.com/)
xMule (http://www.xmule.ws/)
XNap (http://xnap.sourceforge.net/) Propritary-dependant (Sun Java)
LPhant (http://www.lphant.com/index_eng.php)
Sancho (http://sancho-gui.sourceforge.net/)

KDrive

KDrive (http://www.kdrive.com/) Proprietary

FastTrack

Apollon (http://apollon.sourceforge.net/) - uses giFT
XNap (http://xnap.sourceforge.net/) Propritary-dependant (Sun Java)
MLDonkey (http://mldonkey.org/)
Sancho (http://sancho-gui.sourceforge.net/)

OpenFT

Apollon (http://apollon.sourceforge.net/) - uses giFT

Gnutella/G2

XNap (http://xnap.sourceforge.net/) Propritary-dependant (Sun Java)
Apollon (http://apollon.sourceforge.net/) - uses giFT
MLDonkey (http://mldonkey.org/)
Qtella (http://qtella.sourceforge.net/)
Gnewtellium (http://gnewtellium.sourceforge.net/)
MUTELLA (http://mutella.sourceforge.net/)
GTK-Gnutella (http://gtk-gnutella.sourceforge.net/)
FrostWire (http://www.frostwire.com/)
LimeWire (http://www.limewire.com/) Defunct/Deprecated
LimeWire Pro (http://www.limewire.org/) Defunct/Deprecated
Phex (http://sourceforge.net/projects/phex/)
Sancho (http://sancho-gui.sourceforge.net/)

LimeWire were sent a Cease-and-Desist letter by the RIAA, but instead of closing the client entirely as many others have done in the face of such notices, they have decided to filter copyrighted content within the client. If you use LimeWire to acquire copyrighted content, we recommend you do not upgrade. More details can be found on Slyck.com. A new P2P client based on LimeWire's source code has just been started, called FrostWire.

LimeWire Pro is basically the same client, but with a fancier look, no "nag screens", and it searches for new sources more often. If you want it, we suggest you compile it from source instead of paying for it.

Also, please note that the Gnutella network has nothing to do with the GNU Project. The Gnutella name was chosen randomly by it's author.

OpenNap

Lopster (http://lopster.sourceforge.net/)
XNap (http://xnap.sourceforge.net/)
TekNap (http://www.teknap.com/) - Site Offline.
WinMX (http://www.winmx.com/) WINE Proprietary
gNap (http://gnap.sourceforge.net/) - Project Closed.
Apollon (http://apollon.sourceforge.net/) - uses giFT
- giFT-OpenNap (http://developer.berlios.de/projects/gift-opennap/) Defunct/Deprecated

DirectConnect

WinMX Peer Network

WinMX (http://www.winmx.com/) - Defunct/Deprecated - WINE - Proprietary

Frontcode Technologies, who wrote WinMX were sent a Cease-and-Desist letter from the RIAA, and closed the entire network by shutting down the peer cache servers that WinMX used for getting primary IPs. Some Italian coders created a workaround and set up their own peer cache servers - details can be found on Slyck.com.

To make WinMX work, download this file and place it in your WinMX folder. If there already is one, replace it.

If you don't know where to download WinMX, you can grab the last version ever released - 3.54 Beta 4 - (Standalone .exe file, no installer or other accompanying files) here.