I know we have DeaDBeeF which is cool and similar to foobar2000 but one of these days I stumbled upon a music player backend named MPD (Music Player Daemon - http://www.musicpd.org/).
Excellent for very small projects where hdd space and RAM are very limited. Like a raspberry Pi or an old netbook.
It has several CLI and GUI clients.
Two of them amazed me:
ncmpcpp (ncurses based - http://ncmpcpp.rybczak.net/screenshots.php)
gmpc (gtk2 based - http://gmpclient.org/screenshots)
One of these days I'll give them both a proper run on their features&robustness and will post back here.