I'm so happy to see so many people mention Hotline in here! Aahhh the good ol' days :) Indeed, when Napster came along, it wasn't too surprising to me .. that is, other than the true p2p nature of it, rather than server/client/tracker. That was indeed awesome. But there was also a bit less accountability so you got a lot of sketchy/crappy stuff, whereas hl servers (and users) had somewhat of a reputation to uphold (IMO).
I tried really hard to get into Hotline, I still remember the "welcome to Hotline" girl. Every hotline server I tried was either terrible or so full it was impossible to connect or use. Never had a good experience with it. Guess I wasn't in the loop enough.
Curious if any P2P networks existed before Hotline. I recall using it briefly before Napster burst onto the scene, and always considered it to be the pioneer.