Should you prefer to use Winamp, this video will explain how to set up and use Winamp to stream music or voice into Second Life.
You can find Winamp here: http://www.winamp.com/
butt (broadcast using this tool) is a lightweight, easy to use, multi OS streaming tool. It supports ShoutCast and IceCast and runs on Linux, MacOS and Windows. This video will show you how to set up butt on Windows to stream into Second Life.
You can find butt here: http://butt.sourceforge.net/