I second the pirate bay and demonoid. I usually hit the Bay first, and Demonoid when I can't find anything on Pirate Bay.
ilovetorrents.com is a great private tracker, try to get signed up there. If you can't find something there go to thepiratebay.org .
I thought the people closed down The Pirate Bay. Because in the news, these 2 adminstrators of this site is sentenced to 1 year in prison for hosting Torrents (True story ).
I heard about the pirate bay thing too, I was planning to join them but the site might be watched now it has the rep... I use mininova.org (not .com, fake) or demonoid, but stick to mininova since on demonoid whatever torrent I download it comes up as "invalid torrent" which drives me nutz! Plus mininova don't require signing up which is good, except when you find a private tracker on the site, meaning if you want that one you have to join the torrents original site...not minonova.
Porno graphic material is banned on that site from what I have read of the rules, and all the torrents I got from there have all been great, sure some music files were a tad...crap compared to what you would find in stores, but what do you expect, least I have something I can't get here in australia 'ay mate XD (But most have been good otherwise, just the one selection that had "boot leg" as part of the description)
Mininova.org, Torrentz.com and Iso Hunt. Those are the ones I frequent the most. Mininova doesn't have porn on their site. As for the next two...eh, can't say the same.
ISOhunt is a great torrent site. Could also just google what you are looking for followed by the word torrent. For example: "KoRn torrent" and you will get a whole bunch of torrents from various sites.
I was checking out Seedpeer, but, damn....it always takes forever to load on my connection and also, the connection to the site always gets interrupted, resulting in me having to reload the web page...no wonder no one mentioned it here...