Sadly, Winamp went completely downhill from here (IMHO) and the subsequent versions never felt as minimal as this version. AIMP[0] comes pretty close and is a good enough clone of winamp if you're interested.
[0] - http://www.aimp2.us/
I loved how minimal and fast it was. You didn't need to import and manage your media, just drag a folder onto it and blam, it's playing. Nice keyboard shortcuts, no extra crap.
So much of my music is still just folders of mp3s in /artist/album/*.mp3 format and I really can't be bothered importing it all into iTunes, meaning I just listen to the same few dozen albums I do have in iTunes.
These days I more often just drag the folder into the VLC playlist or even use an old version of Winamp if I just want to shuffle through everything or make a playlist. The idea that my music is "in" the media player is something I could never get on board with. The media player is just accessing files in easily located folders. The way iTunes and some others try to hide that fact bothers me on some weird curmudgeonly level.
I chose to let it manage the files but reduced some of the folder nesting. It doesn't obfuscate file names and you can elect for Artist > Album > [file] structure or whatever your heart desires.
And of course, if you're on Unixen, XMMS is pretty much a direct clone of the old Winamp (and used to even use the same skin by default).
I think we should agree it's highly customizable, both for function or style.
http://www.zophar.net/music.html
Audacious comes close, but isn't quite there. PSF2 support is mostly non-functional, for instance.