Shareaza is a luxurious and sophisticated file sharing system application. It can harness the power of up to four separate Peer-2-Peer (P2P) networks, including EDonkey2000, Gnutella, BitTorrent and Shareaza's native network, Gnutella2 (G2). Of course, being a multi-protocol application, it handles several networks, but none perfectly. Their ed2k support is specially awful.
Not only that, but Shareaza is completely free (starting from version 2.0, it is released under the GNU GPL) and won't show any annoying ads or pop-ups. It won't install any unwanted third party programs that can wreak havoc with your computer. No spyware, no registration, no "paid version". Just download and use. Simple.