Mac/Linux: Most BitTorrent clients work just fine at grabbing and managing your downloads. Downpour is a highly customisable installation that works hand-in-hand with your chosen media centre, automatically importing media and supporting your filing and renaming preferences.
It's not a click-and-go app, as the easiest installation requires having a Python implementation set up. But tinker with Downpour enough, and its specialist features will reward your investment. RSS monitoring, automatic unpacking and renaming schemes, a built-in media browser, and a clean, remote-access friendly interface, to start with. The planned features look pretty nice, too.
Downpour is a free download for any system that has Python and a command line up and running; that can include Windows through Cygwin, if you want the hassle. Hit the link to get installation instructions.