I go to a bunch of BitTorrent sites, such as Demonoid & The Pirate Bay, when I'm looking for something specific. There are also a bunch of unauthorized artist-specific sites to download concert recordings, etc.
I also subscribe to about a hundred different music blogs via my Google Reader and download a wide variety of stuff from the wide variety of blogs (lots of old-school soul & funk, blues, etc.). For example, the "Blackness" series at "My Favorite Sound" has been superb.
I have never used Limewire, Napster or any other similar services/sites.