I don't think apple has released a x86 port of OS X yet. I know they intend to, but even then I think it will be designed to solely work on apple-produced hardware.
Thanks for the info. Can anyone here who has used the Windows emulator tell me how good it works? Can you run any windows program on it?
Emulators sacrifice processing power for functionality. My roommate tried getting Half Life:CS to work on a Mac and failed. A ballpark (not verified) for the emulator would be programs taking at most 35% power on an "equivalent PC." Mango's link would probably be your best bet until Apple releases their Macs on Intel processors.
If you're going to use virtual pc for a mac, don't kid yourself and think you can start playing all sorts of pc games on it because the processing power is non-existant. However, if you have some smaller windows programs that you still like to run, then it can really be helpful. I use it on my ibook now and then but don't expect much from it.