Songbird is a Web player built from Firefox's browser engine. Songbird is open source, will run on Windows, Mac OS X and Linux and supports user contributed, cross-platform extensions. Oh yeah, and they're using Drupal.
About the author, Nate Haug
Nate Haug is an ace-of-trades with wide-variety of Drupal skills. He joined Lullabot in 2006.