You'll want to use pkg_install the following:

• audio/darkice - Encodes audio from the sound card and sends it to the Icecast server.
• audio/icecast2 - Serves up the web stream.
• audio/streamripper - Saves the web stream to files. We use this to build the program archive.
• www/lynx - Terminal web browser, this is optional but it helps verify that Icecast is setup correctly.

The following pages will walk you through the configuration of these packages.