Then go with Shoutcast if you want to stream MP3s... it's as simple as downloading a small DSP plug-in for WinAmp 2.xx, configuring a few server settings (only has to be done once), queuing up your tracks in the playlist and hitting Play.
You need access to a Shoutcast server, you can run it on your home PC if you have the bandwidth but I don't recommend it. Instead what I do is have a dedicated server running the Shoutcast free server app. In the DSP plug-in I connect and stream to that server, the clients then connect to the server and play the stream.
The above is assuming a live stream. To stream on-demand you simply upload your MP3s into the Shoutcast server's content directory and the links to the files will be something like http://shoutcast-server:port/content/afile.pls
WinAmp is the suggested player of course but WMP, RealOne and MMJB will also play the streams.
For more info visit http://www.shoutcast.com/
or the discussion forums at http://forums.winamp.com/