I've streamed audio in the past, using Icecast / IceS ( http://www.icecast.org/
). Worked really well; lets you stream from any source you like (mic, lines, pcm, ...).
Takes some configuring and if you find that everything seems to be properly configured/running, but you can't connect (!!!) be sure that whatever source you're using has a volume setting > 0 (sounds obvious, but it was the last place I and many others looked -- you'd think it would still be possible to connect to the server, but NO