P2P Clients
"P2P clients like Grokster, KaZaA, Limewire, Morpheus and eDonkey do not make a P2P Network; they only allow the user to connect to an existing network by using common protocols. There are a large number of P2P networks out there: Gnutella, Gnutella 2, Ares, FastTrack, eDonkey2000, BitTorrent and even Freenet. Clients are applications used to connect to those networks. [...]"
From http://www.readwriteweb.com/archives/skyrider_and_p2pfuture.php