I’ve gotten to rather like qmmp. It offers a nice balance of simplicity and functionality, and has the added benefit of being modeled visually after my favourite windows based media player, winamp. To make this style more complete, i’ve added the official Winamp base skin.
The classic skin came from here. Just download the .zip and place it in ~/.qmmp/skins, open up the settings, make the switch, and you’re good to go.