No, this is against Apple's licensing and therefore illegal. The ONLY exception is for Leopard Server version, running on Apple hardware (via Fusion, or Parallels' product).
Perhaps someday in the future, Apple will get their head out of the sand, and decide that they would like to be a software company which actually makes money, and desires market share. But up to and including now, every single decision they have made have been financially the wrong ones in this regard. If they would allow their OS to be installed on any computer (including virtual ones), they would probably outsell Windows and any other OS out there. But, they must love being the runt/underdog/whatnot...
