Update: Original version of this post contained some accidental misinformation. Errors have been corrected.
Azureus was my Bittorrent client of choice back in the day -- it used to be open source and easy to use and install, and served up any torrents you'd like. Eventually, however, the app was turned into Vuze, got put under a much more restrictive license and added a bunch of extra content bloat, and I abandoned it in favor of the much simpler µTorrent (unfortunately, it's not open source either, but you can't win them all). Now, however, it sounds like Vuze is trying to make things a little easier on their customers -- the restrictions are still there, but you can now watch any or all of their content on any or all of your devices, including the iPhone and iPod touch, the Apple TV, and even consoles like the PS3 and the Xbox 360.
It's only slightly easier -- everything still has to be downloaded under the Vuze umbrella, but with just an option, you can drag and drop into iTunes or onto any of your other devices and then sync things out from there. If you do choose to access content through their application, at least you'll be able to bring what you download out onto the other devices you own.
You can download Vuze over on their site. Downloading content from their network can be done with just the app, though using their comments and Friends system will require a free onsite registration. The device integration currently only works in OS 10.5, though they're working hard to make it possible in 10.4 as well.