Zippyy, I was responding to your original statement that the AE has only USB out.
The devices Gmood1 sent links to don't connect to the USB port on the Airport Express, they connect to the USB port on your PC or Mac. To get an audio signal from the Airport Express you can plug either an optical cable or a stereo mini analog cable into the single audio jack on the AE. It's a dual-purpose port and either an analog cable or optical digital cable will work as long as you have the right size connector on the cable. The USB port on the AE does not provide the same audio-out capability as a USB port on the computer.
The devices Gmood1 sent links to don't connect to the USB port on the Airport Express, they connect to the USB port on your PC or Mac. To get an audio signal from the Airport Express you can plug either an optical cable or a stereo mini analog cable into the single audio jack on the AE. It's a dual-purpose port and either an analog cable or optical digital cable will work as long as you have the right size connector on the cable. The USB port on the AE does not provide the same audio-out capability as a USB port on the computer.