It is now possible to do Live audio streaming to an icecast server from Mac OS X. Under Mac OS 9, there was SoundJam, but under Mac OS X, I didn't find any software to do live streaming. The solution is to use some UNIX open source projects. Read the rest of the article for the details (the Developer Tools are required to compile some of the required UNIX code)...
conn.ip = "xx.xx.xx.xx";
conn.port = 8000;
conn.password = "hackme";
conn.mount = "test";
conn.bitrate = 128;
% esdrec | lame -b 128 - - | ./exampleThis will grab your sound-in (I've tested Mic and Sound-In on a new PB 800 MHz), pipe it to the MP3 encoder, and send it to the icecast server with "example".
http://xx.xx.xx.xx:8000/testAnd hear the stream, quality is perfect and in total it uses less then 30 % CPU power for encoding.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020704134818926