Just found this at http://hp.vector.co.jp/authors/VA032810.

Play's Ogg files as well as mp3's, and handles .pls and .m3u playlists, and Shoutcast - not sure if there's something already out there that does this and is free, but this is the first i've found. Also not sure if it'll go with WM5, (i've only got PPC2003)