accessTunes

$15 buys you access to your iTunes Music Library from anywhere via the internet.  Check out
accessTunes from Bains Software: "accessTunes starts sharing your iTunes Music Library as soon as you turn on your computer, making it available as a shared iTunes library on the local network, and accessible from anywhere in the world via the Web....With accessTunes, you can listen to your roommate's music even if he doesn't have iTunes open, or listen to music from your home computer at work, even if you're on a PC."

Nice. The demo will work until you stream 50 songs, then you'll have to pony up the dough.