DeaDBeeF (as in 0xDEADBEEF) is an audio player for GNU/Linux systems with X11 (though now it also runs in plain console without X, in FreeBSD, and in OpenSolaris).
Guayadeque is a music management program designed for all music enthusiasts. It is Full Featured Linux media player that can easily manage large collections and uses the Gstreamer media framework.
Clementine is a modern music player and library organiser. Clementine is a port of Amarok 1.4, with some features rewritten to take advantage of Qt4.