Shareaza - 2.5

Shareaza has unique features, including ghost ratings, a completely user-configurable queue area, and multinetwork support. The program started as a Gnutella client but recently branched out and developed Gnutella2, a completely open and documented network. Shareaza's interface is easy to use, yet powerful and fully skinnable. Shareaza's download core was built to provide optimum performance from any number of sources. Shareaza can manage your download queue automatically, or you can take charge and modify the status of files or even individual physical transfers and sources.

It won't install any unwanted third party programs that can wreak havoc with your computer. No spyware, no registration, no "paid version"