Porthole

Porthole is a tool that lets you stream the music from your favorite music player such as Spotify or Pandora to your Airplay speakers, Apple AirPort Express and Apple TV.
Porthole focuses on being elegant and simple to use.

The setup wizard will have you going in no-time. De-cable your living room and start enjoying wireless music throughout your home.
Porthole can stream to multiple speakers at the same time, allowing you to stream your music all through your house, in sync!