Build a networked music player. It will be wired or wireless, fetch music from a central server, and play mp3, ogg, and other formats. Commercial examples are many: Tutle Beach's AudioTron, BAR[IX] Exstreamer or Exstreamer Digital, Squeezebox or SLIMP3 from Slim Devices, the Rio Digital Audio Receiver, and others.
Moro MC
http://moromc.dyndns.org/article.php?story=20040105163020906