Vuze is the free, full-featured reincarnation of the popular BitTorrent client Azureus, an app for finding and watching video content that you download via torrent files.
Compared with more traditional and utilitarian BitTorrent clients, Vuze has a much richer, iTunes-style interface--with as much attention devoted to finding and viewing videos as to downloading them. You can browse the "Vuze HD Network" for videos (although you'll find a lot of lower-grade Internet fare, like promos, trailers, and podcasts), or you can look around using a friendly, easy search interface (although much of the content you'll find is copyright protected, which Vuze warns you about). The download functionality is excellent and fast, with plenty of control over even esoteric settings--and it's easy to view technical minutiae for a torrent in Vuze's big visual interface. Vuze will also help you get video into your iTunes with a beta "Devices" feature, and even onto your Apple TV, iPhone, iPod, or other devices.
For someone new to torrents, Vuze could be a great, easy introduction. If you're already familiar with using torrents and you're happy with your current client, you might not find enough here to inspire a switch.