>>15
Well, there's mplayer... mikmod, oggplay, etc. etc.
But one thing I haven't tried but I heard is uber leet is "MPD"
http://www.musicpd.org/features.shtml

There's a ton of front-ends (just click "clients" on the site)... web front-ends, bash integration, an ncurses client, a bare-bones terminal client, graphical clients, etc.

The idea being the music player just runs as a daemon, like a jukebox, and you use the front-ends to control the playlist dynamically. Pretty tight.