Winamp 5 works fine on Vista for me. For no-bloat mp3, try 1by1. It's good if your music is well organized on your hard drive, if not it lacks a typical music library so it may not be for you (btw you can get folder view in winamp by using the dynamic library plugin).
Xmplay is pretty minimalistic (like Winamp lite), but personally I only use it for MIDI
MediaPortal is like Windows Media Center, but Open Source. Since it does alot more than play audio, it may not meet your definition of non bloatware, but I just thought I'd through it out there as an option