Mac: Audiozue is a minimalist app that sits in your menubar and gives you quick access to all your music sources, including iTunes, Spotify and Rdio.
On top of offering simple controls for all your favourite music players from the menubar, Audiozue also shows you the songs you listen to frequently. If you want to share your music listening habits, Audiozue connects to Facebook, Twitter, Tumblr and Scrobble. Audiozue is a simple tool and perhaps a little expensive, but it works well and is unobtrusive when you're not using it.
Audiozue ($5.49) [Mac App Store]