I found that Morpheus, Grokster, Kaazaa, all use the same network, and were pretty good some time ago. Now however, the searches seem to get bogged down and the things that I look for just aren't there, or my searches don't get to them. Same with bearshare and the different services that use that network.
I have been using audio galaxy lately and it seems to have more of the obscure stuff that I like than the others. This includes 20s and 30s jazz as well as jug band music and novelty songs.
I read somewhere that some of the networks get bogged down by too many users. Maybe that is what is happening.