Many hardware devices like Slim Device's Squeezebox and Roku Labs SoundBridge allow for playing audio out from your machine to a stereo system. Apple's AirPort Express is also a popular choice, for which we developer our Airfoil software. However, for sending any audio to devices like the Squeezebox, you'll want to use Nicecast. With Nicecast, you'll be able to play Windows Media, Real Player, and even protected AAC audio through your hardware device. Read on for more details.
Setting this up is pretty simple. We'll be using the Squeezebox for our reference, but all these instructions should apply to the SoundBridge and other devices as well.
1) Open up Nicecast, and set your desired audio source. This is the application that will play the audio you wish to hear through the Squeezebox. Then click Start Broadcast.
2) Open up iTunes, and choose Open Stream from the Advanced menu.
Enter your machine's local network address in this form icy://10.0.0.1:8000/listen. This can generally be found in the Share drawer of Nicecast, next to the world Local. Click Ok, causing the stream to play in iTunes. A link to the stream (with your broadcast's name) will also be saved in the iTunes Library.
3) From the Squeezebox, you'll be able to tune in directly to this stream.
That should be all you need to do. Any audio played through Nicecast, from an application such as RealPlayer, Windows Media Player, or even iTunes (for protected AAC) will then be available through the Squeezebox. Enjoy!