Mac: One of the coolest parts about Apple's AirPort Express router is wirelessly playing music from iTunes through speakers all over your home. With RaopX, however, you're no longer limited to iTunes; you can play any system audio through AirTunes.
In order to play audio through your AirPort Express, you'll need RaopX and inter-application audio router Soundflower. After installing both, all you need to do is go to Sound in System Preferences and change your default input and output to "Soundflower (2ch)" and start up RaopX in a Terminal session (just launch Terminal [Utilities -> Terminal] , type in RaopX, and hit Enter). RaopX will build a 9-second buffer and then stream all audio from your computer to any speaker connected to an AirPort Express.
It's certainly not as easy as picking "AirTunes" from a drop-down menu, but it's hard to complain when you can finally stream Mixtape.me or your other favourite non-iTunes media player to AirTunes. Note: RaopX does not currently support Apple TV or iTunes Speaker Passwords.
RaopX is a free download, Mac only.