you need winamp, and edcast, on your end. at the bare minimum.
and you also need a shoutcast or icecast server to stream to, and that people can listen from. for the most part, those are not free. try not to buy one that bills for 95% percentile of your max listeners, or by the # of total slots. always try to get them billed by the actual bandwidth you use, and shop around for how much bandwidth should cost.
there's tutorials about how to do all this all over the web, google is your friend, and we are too.
