Mostly mIRC and the occasional BitTorrent. I used to use Kazaa and then K++, but everything I got using those progs I can get from mIRC with less hassle.
About Soulseek: The only thing that keeps me from using it is the fact that just about all of my friends that have used it in the past ended up with viruses on their computers. Might be a coincedence, but a very big one. Not saying the program itself contains a virus or anything, but I would suggest being very careful when downloading files using this particular P2P solution.