Torrentleech.org Pm me your email if you want a invite (only 0ccul7).
Depends on what you're looking for. As mentioned, IPT is a good general purpose tracker but it's really easy to obtain an invite so it's not all that private. Still better than public trackers though. For music, what.cd is great, TehConnection for movies, GGn for games, MAM for books/audiobooks, BitMe for e-learning. There's pretty much a tracker for every niche.