I had been searching for something to do this for a while, everyone said it was something that is only easily done in UNIX.
It allows you to play something on "computer 1" and hear it on "computer 2". Not just files, streaming, anything. wireless or hard wired.
I just found it today, it allows me and my dad to play something on our laptop, stream it to the media center, and the media center automatically sends it to the living room stereo.
So I don't have to get up, and go change the music/station/whatever on the media center. I can control it from my laptop, wireless.
There is however an approximately 2 second delay depending on the quality of the sound.
I, personally, think this program Rocks!
Link
http://www.vypress.com/products/tonecast/