One of the nice things about the combination of iTunes and the Airport Express is the ability to stream audio content from your Mac to another room. It makes having outdoor parties a whole lot easier to set up.

The problem with this, however, is that the audio is limited to your iTunes Library. What if you were streaming some audio via Safari, or wanted to wirelessly stream audio from a movie on DVD? There is a 3rd-party application that fills in the gap here. It's called AirFoil by Rogue Amoeba.

Basically, AirFoil works just like iTunes in that it allows you to send audio to remote speakers via your Airport Express. In addition to using iTunes, however, it also allows you to use audio from any application or input on your Mac... even system sounds! But wait, there's more! It also allows you to send that audio stream to not just one Airport Express, but multiple Airport Expresses. So if you have several Airport Express stations around your house, you can stream the same audio to all of them simultaneously.

To download AirFoil, click here. Once you have downloaded and opened it, you will see something like this:

The user interface is pretty self-explanitory, so I won't go into details. The trial edition allows you to use the fully-functional application for up to 10 minutes. After that, a noise is then overlaid with the audio. It's just enough to annoy you into buying it, but if you like what you hear (before the noise, of course), then the $25 price tag is probably well worth it.