Linux

Audio Galaxy
http://www.audiogalaxy.com/
Search user collections at their own machines and a web based search through user's personal online collections, which resides on the Audio Galaxy servers

eDonkey 2000
http://www.edonkey2000.com/
eDoney 2000 is a multi platform file sharing tool with it's own network. It can find any type of file, resume downloads, get one file from different sources simultaneous and has many more advanced features.

GTK-Gnutella
http://gtk-gnutella.sourceforge.net/
Gtk-Gnutella is a clone of Gnutella which needs GTK+ (1.2 or above). It is currently developed and tested under Linux (Debian 2.2).

File Rogue
http://www.filerogue.com/
Windows 95/98/ME, Windows NT, Windows 2000, Linux, Unix, Macintosh

Gnut
http://www.gnutelliums.com/linux_unix/gnut/
Gnut is a command-line client which implements the gnutella protocol. It supports all features available in the original Nullsoft client, as well as many others.

Hagelslag
http://tiefighter.et.tudelft.nl/hagelslag/
Hagelslag is an implementation of GNUtella. The main goals for this implementation are flexibility, stability and performance.

INoize
http://www.inoize.com/
This is music sharing software with it's own network that prides itself for organizing the files by artist, Album and Title

Mojo Nation
http://www.mojonation.net/
Mojo Nation is a revolutionary new peer-driven content distribution technology, or so they say. It's software with a business plan, check it out!

Freenet
http://freenet.sourceforge.net/
Freenet is a large-scale peer-to-peer network which pools the power of member computers around the world to create a massive virtual information store open to anyone to freely publish or view information of all kinds.

OnShare File Manager
http://www.onshare.com
This is a multi-platform p2p network written in Java

Gnutella
http://gnutella.wego.com
This website is the home of the software based on the original gnutella client by Winamp's Justin Frankel.