curaga: You're right - the old legacy XMMS might be an option here.
As I stated I'm not searching for a console application - I know there are some of them, but if I go for console I'm content with mplayer
mplayer -playlist <(find "$PWD" -type f)
That little snippet creates a playlist from the working directory and plays it in mplayer.
I don't need such an application build any kind of music database for me because I have my files organized in a very straigt forward way (Interpret/Album/*) and mostly listen to albums as a whole.
As others, I've got this fancy geek dream of a system which is full featured but very lightweight. Tinycore is a very great step in this direction!
I'm working with embedded linux systems and so I'm really stunned every time I work with a current Windows7 system which is almost 10 GB out of the box. If you let windows update work a bit and install MS Office you've about 20 GB filled with worthless crap.
Maybe a FLTK frontend to mplayer would be useful, but on the other hand - why has noone done this before?
It doesn't sound very hard to me to get some basic functionality working in little time.
Edit: typos