I don't download from torrents any more but I used to use utorrent, I now download from Rapidshare because it is faster and more secure because you don't have to connect to multiple IP addresses and you don't have to forward and open any ports on your Router. You can find just about any thing on rapidshare on google by searching "rapidshare.com I want this"
I use Rapidshare, Megaupload, etc. more these days too. There is more variety, at least, for what I use it for. I'm a free user so torrents can be quicker for me.
aria2 on Linux, Free Download Manager on Windows - they can handle metalinks, torrents, and multithreaded downloads.
BitTorrent, the client. Surprised it isn't up there - but then isn't it pretty much a clone of uTorrent? At least to me it seems.