And a surprising number of people now use Spotify or Pandora for their primary music interface.
Most people that I know use foobar2000.
Yeap, foobar2000 is basically the "standard" now.
iTunes and WMP, mostly.
To be honest, I don't know what else people are using. It's one of the places I've had to do the least research in software. WinAMP has been a stalwart for over a decade.