If you use AirTunes, don’t walk – run – to http://RogueAmoeba.com and download AirFoil right now. This $25 application liberates that handy little Airport Express from iTunes slavery and lets it play music from any application on your computer!
I have been needing something just like this for months. I would have paid twice the price for something that works this well. (But don’t tell Rogue Amoeba that – they make tons of great, cheap Mac applications. (They do Windows too, but who cares?))
Bonus audio-related link: FrequeNC has tons of free MP3s of interesting local (Chapel Hill) bands. Enjoy!