Awesome bittorrent client: http://www.bitcomet.net/
http://www.filelist.org/ | Good site, open registration (for now), ratio based seed/downloads. Has all kinds of shit, recommended.
www.filemp3.org | Sister site to filelist.org, open registration (for now), ratio based seed/downloads. All mp3s of all kinds. Some pretty rare and obscure shit at times. Recommended for the audiophile.
http://www.torrent-damage.net/ | All kinds of different stuff, games, movies, music, good site. Currently is closed registration, and I have no tickets #s available atm, but you can go to their mIRC channel and beg for one. It's worth it.
http://isohunt.com/ | Torrent indexing site, larger indexing than the late great Suprnova had at it's peak. Already under MPAA radar, so don't expect it to be around forever. I like it.
http://www.mininova.org/ | Pretty big site, all different stuff, anime, porn, movies, games, a rather large amount of eBooks. Getting a little too big and noobish (like Suprnova did). Will probably be under watch soon, if not already, so I don't really fuck with this site too much. Even so, you can find some good stuff here.
That's all i really get down with. Bittorrent is under fire right now, feds are involved and shit, so I limit myself in what sites I use now. You should too. I advise you don't download high publicity releases of movies and games, until (or unless) a reputable group releases it. Know the difference between rips and propers, divx vs dvd rips, what a nuked release means, and which groups do REAL propers. It will save you trouble in the long run.
And always, always, fucking seed your downloads (unless it's from somewhere huge and red hot gay like mininova, fuck that site). 1:1 is always an acceptable ratio.