Personally, I've always used IRC (Internet relay chat).
there are servers/channels with 'bots running xdcc scripts.. for that.. i used a piece of software called "xdcc catcher"

I also use phazenet for mp3's and use "autoget", a script for mIRC which is pretty cool.

I've got different servers on my network doing different things.. but also.. a very untapped resource are newsgroups... not for the faint hearted.. but good once you get the hang of things

Disclaimer: Of course... all mp3's downloaded are always removed from my servers within 24 hours (as per the legal requirement) and all films are actually trailers in which I evaluate the film and decide wether to go and see it at the cinema or not