You can also build an open-source frankenstack for free. It’s just four pieces: Soundflower, Jack, Darkice and Icecast. This post explains how to put these pieces together.For those who are interested, this is pretty close to my setup for Rebuild.fm Live stream: Skype — Soundflower -Jack — Darkice.
I was about to purchase Nicecast which eliminates all of these pains to install them, replacing with its nice UI. But having installed jack and darkice, beginning the stream is as easy as running a shell script via SSH.