I've written some software which does live mp3 "radio station" type streaming. Listeners can choose what songs they'd like to hear via the web or an IRC bot. They can also submit URLs, and the server will fetch the mp3 and stream it out to everyone. Each user has a specific queue and equal priority when it comes to who's song gets played next. A buddy of mine is working on a mysql index backend which will be pretty cool too. Oh yeah -- its all written in perl.
My software differs from shoutcast in that it doesn't re-encode the mp3s it streams out. It just reads pre-encoded files off the disk and streams them out to everyone. You don't need a winamp frontend to make my stuff work, tho you can't do voiceovers as easily as with the shoutcast stuff.
I'm probably going to package everything up and release it for people to play with. Anyone interested?