Good places on the internet - Soulseek (http://www.slsknet.org/)

Soulseek is a peer-to-peer file sharing network focused on music, started in 2000? (I dont trust the dates online)

Soulseek for me is the closest thing to a dusty 2nd hand record store on the internet, in the great P2P tradition (shouts to KaZaa and Limewire too). For out of print recordings, bootlegs, bloghouse cuts, or old school music privacy it is unmatched and has survived, probably due to it's P2P pipes and niche taste.