So, I finally got around to writing a plug-in for xmms that uses libmad.
http://superduper.net/cvsweb/cvsweb.cgi/xmms-mad/
http://superduper.net/xmms-mad/
Right now it can play files or shout/ice streams.
Seeking/configuring/fileinfo/length estimation are all missing.
If anyone wants to out I would welcome contributions. I think I will steal the file info and configuration dialogs from the mpg123 plugin.
sam