Mac OS X on VirtualBox
VirtualBox can run Mac OS X as a guest.
But you have to download a hacked version of the Tiger (or Leopard), then you have to:
- disable acpi on virtualbox
- enable VT-x/AMD-v on virtualbox (only recent processors supports them)
- pass the param 'platform=x86pc' on the command line before booting
(one can also edit the file /Library/Preferences/SystemConfiguration/com.apple.Boot.plist to get the same effect)
Then OS X should start without any problem and it should run very well (it does, on my intel e6300 with 2GB RAM)