kazaa lite, winmx (in the past), limewire (in the past), and soulseek, not many people know about soul seek. so www.slsknet.org check it out. It's more like the early napster than any other p2p I've ever used.
It has a central server...I guess it still qualifies as p2p though.
E-Donkey has a small ad banner in the top right corner. It doesent bother me because it stays out of the way. And i dont think it has spyware or else my ad-aware and spybot search and destroy would have caught it.