Is there a way to stream the same playlist on multiple computers at the same time? I want to be able to sync what's playing on multiple computers (for parties etc).
Perhaps you should have a look at Airfoil:
Send any audio from your PC to AirPort Express units, Apple TVs, iPhones and iPods Touch, and even other PCs and Macs, all in sync! Airfoil for Windows gives you your audio, all around the house.