Without a doubt, the BitTorrent network is one of the most popular file sharing methods at the moment. The most significant and probably most peculiar difference between BitTorrent and previous generations of file sharing is the "one file, one network" structure. Instead of trying to create one big network of files using SuperNodes, web caches or servers, BitTorrent creates a new network for every set of files. Servers running tracker software keep the small networks online...
These guides will help you if you've just found out about BitTorrent.
These guides will help you with things when you're already familiar with the BitTorrent basics.
These guides help you along with your own BitTorrent site.