Use airtunes for anything!
I love the iTunes/AirTunes combo, so much so that I have manage to get the office to buy Airport expresses as access points but i have always felt annoyed that you can't use them for any music, just iTunes music.
This means that I am stuck when it comes to listening to my last.fm stream, it doesn't come into iTunes, so headphones it is. Until I found this nice little hack/app called airfoil - it hijacks the audio stream that come from the last.fm player and sends it straight to any airtunes speakers! How cool is that?
Ok, so it is not free but $25 is not much to ask for audio freedom

Any help is highly appreciated,
JAN