Some of these include "Limewire", "Morpheus" and "Warez". Just go to whatever site and click the "download now" option but make sure it is the FREE version you are installing!
You will then, after installing, have a program that allows you to type in the name of a song or whatever, search for it and then download it.
I would recommend reading what they have to offer first before making your decision, as some are better than others.
Actually, there’re many online downloaders available on the
web. But many of them are not supported anymore by Chrome or IE. I’m currently
using a nice desktop program that can detect and download video clips
automatically. Maybe you will find it useful as well.