The September issue of Linux Journal has an article titled "Internet
Radio to Podcast with Shell Tools".

The author uses mplayer to do the capture and then created a perl
program embedded in a bash script to create corresponding XML
information.

the resources for the article can be found at
www.linuxjournal.com/article/8402 and if you have registered, the
article http://www.linuxjournal.com/article/8171

- Jay