Just discovered the PearPC project on Sourceforge, then found this quick review via Slashdot:
While the emulator is very much in its infancy, I can't wait to have all three major OS's and every major browser running on my test box
At the moment it appears pretty unstable and the processing power of the emulated mac is approx. 1/5 of the host
But who cares, it exists now, and can only get better!