Top 6 Torrent Sites:

1.The Pirate Bay: The web’s largest collection of bit torrent trackers. The PirateBay banks on its member file sharers to cull the web’s torrent files and makethese available to users.

2.Mininova.org : What started as an alternative to the now defunct Supernova that went offline in 2004,Mininova has become the biggest torrent searchengine and directory on the web. The site provides easy-to-use directory and search for all types of torrent files.

3.Torrent Portal : This P2P and file sharing site works like Google by linking only to .torrent metafiles and captures the caches of those files. It does not store files nor transfer data which are content linked to by .torrent files.

4. Alive Torrents :Alive Torrents is a relatively new site. It has a good collection of torrents,having a solid swarm base and an active readership.

5.Torrentz: This Sweden-based torrent meta-search engine also indexes various  major torrents sites including Mininova, The Pirate Bay and Demonoid. It provides various trackers per torrent that would work when another tracker is not working.(www.torrentz.com)

6.www.yourbittorrent.com: It has a good interacting interface,easily searchable database and also indicates the validity of the torrents.

SOME OTHER USEFUL TORRENT SITES:

1.www.kickasstorrents.com
2.www.demonoid.com
3.www.entertane.com
4.www.torrentscan.com
5.www.vertor.com

Some Other Links:
All about Torrents!