you can also use airfoil to connect anything that plays on your computer to the airport express.
http://www.rogueamoeba.com/airfoil/
"Airfoil was built with one purpose in mind - enabling you to send any audio you want to Apple's AirPort Express device. Airfoil works in conjunction with your AirPort Express and any audio player. Use it to send audio to your AirPort Express from Realplayer, Windows Media Player, QuickTime Player, or even your web browser. With the ability to send almost any audio to your remote speakers, Airfoil and your AirPort Express make a great pair."
http://www.rogueamoeba.com/airfoil/
"Airfoil was built with one purpose in mind - enabling you to send any audio you want to Apple's AirPort Express device. Airfoil works in conjunction with your AirPort Express and any audio player. Use it to send audio to your AirPort Express from Realplayer, Windows Media Player, QuickTime Player, or even your web browser. With the ability to send almost any audio to your remote speakers, Airfoil and your AirPort Express make a great pair."