Torrent Clients (Downloaders)

the best:
http://bitcomet.com

the rest:
http://bitconjurer.org/BitTorrent/ (The original)

http://www.bittornado.com/

http://azureus.sourceforge.net/

http://pingpong-abc.sourceforge.net/

http://krypt.dyndns.org:81/torrent/index.phtml (command line, great for making your own torrents)

http://sarwat.net/bittorrent/ (Mac OS client)

feel free to reply to this thread with any other clients not listed.