The MIRC has TONS of stuff on it, though lately I've not seen as much. It's a little difficult to use but once you figure it out it's nice.
Of course LIve365 is the way to go if you want the music (to listen online). I have a station but along with mine there are TONS of stations that are great. I know Hopper and some others are really great.
I'm joining the clueless club here too...I have no idea what MIRC is either and I'm really trying to scrounge up some music here. I had a lot from ye olde Napster days. But alas, they are days of yore, indeed!
MIRC is internet relay chat. It is a very basic chat program. You can find some disney oriented chat rooms on it, but need to know some very basic coding to do the file sharing and access some of the servers there.