Bearshare is the best but it had a error in the software where it always closed on me so i went to limewire which is almost as good but i got pro and it kicks major ass.
Yeah, WinMX is not bad either. The good ones are Limewire, Bearshare, WinMX, Ares, Ares Lite. The one to avoid is Kazaa...it only gives you tons of spyware along with your songs...