KPlayer is a decent music player and a front-end for MPlayer.

It's not pretty, but it gets the job done.  MP3's work in KPlayer as soon as you build it.

Download:  kplayer-0.6.2.tar.bz2

Exract the tar.bz2 to a new folder.

Open a konsole in the new folder and type this:

make -f Makefile.dist && ./configure && make && sudo make install