Popular p2p/BitTorrent clients:
BitTorrent (my personal favorite)
Azureus
uTorrent
BitTornado
ABC
BitComet
BitLord
LimeWire
Each Bittorrent client is different, so for the most part your decision is basically going to come down to personal preference.
Torrent file download sites-
( just search with "raw" and/or type the name of the anime as your keyword(s) to find your downloads)
http://btjunkie.org/
http://www.isohunt.com/
http://bt.saiyaman.info/
http://thepiratebay.org/
http://www.downloadanime.org/
http://a.scarywater.net/
http://www.deadgod.net/anime
http://www.boxtorrents.com/browse.php
Here's a few websites that compare various clients.
http://en.wikipedia.org/wiki/BitTorrent_client
http://www.slyck.com/bt.php?page=2
http://www.openp2p.com/pub/t/75
Good Luck !