Limewire is a fast Peer-2-Peer file sharing program (to be used only for the exchange of authorized files).
LimeWire allows you to search for multiple files at the same time, is available in several different languages, and is most famous for its ease-of-use and cross-platform compatibility.
This version for Mac Classic is frozen at version 4.0
Limewire for Mac OSX and Windows also available for download on this site.