I've used soulseek pretty recently! There's a nice client called nicotine, IIRC.
replyThere are message bots that spam you with racist abuse if you're sharing nothing (i.e. not even your downloads), but that's about it.
Oh so pretty much the "classic" share something rule; that was pain in the ass in DC++ times but quality of whatever you could find there was best
replyDC++ now that's some nostalgia.
replyMyself used IRC XDCC bots connected to my 33k modem connected to my 486DX which would disconnect every three hours.
eDonkey, WinMX, lovely fashionable protocols.