Mac: Audiozue is minimilist app that sits in your menubar and gives you quick access to all your music sources, including iTunes, Rdio, and Spotify, all in one place.
On top of offering nice, simple controls for all your favorite music players from the menubar, Audiozue also shows you the songs you listen to a lot (called Trending Songs). This isn't tapped into any service—it's just what you're listening to, which is much more personal. If you want to share your music listening, Audiozue connects to Facebook, Twitter, Tumblr, and Scrobble so you can easily share what you're listening to. Audiozue is simple, but it works well and is unobtrusive when you're not using it.
Audiozue ($4.99) | Mac App Store