I use bitlord and/or utorrent. As for sites www.torrentspy.com www.mininova.org http://torrential.kicks-ass.org
I used to use azureus all the time. Now Ive switched to utorrent as it starts with windows minimised so I can resume seeding automatically and isnt so resource hungry. Not sure what works on a mac though.
i just use flash get with flash got (plugin for firefox) lest me schedule so much easyier, used to use azureus, was good till i started going over my peak lmit in 5-10 days
I think everyone ignored your "for mac" requirements. I think Azureus is probably the best one out these for Mac, but its a resource pig due to being a Java app. Works great though
BitTorrent/TomatoTorrent would be my choice for Mac. http://sarwat.net/bittorrent/ Type aXXo into torrentspy if you want first rate movies.