Songbird is a cross-platform, Mozilla-based music player with high ambitions. The app is still undergoing heavy development, but it has come a long way since we looked at the 0.1 release in 2006. Songbird today can sing a pretty sweet tune, but to push its way into the big leagues, it needs to get over its own interface.
The latest release is 0.25, available for download for Linux, Windows, and Mac OS X. The project provides Linux builds for both 32-bit and 64-bit Intel architectures. Songbird uses GStreamer as its media back end on Linux, but VLC on Mac OS X and Windows, so make sure you have the proper dependencies preinstalled. In general, a Linux system that can run the latest Firefox can probably run Songbird as well.