You mean Max OS X client (i.e., not only the server edition)? That is, machine-specific (retail was only for PPC) Tiger/Intel and/or machine-specific and retail Leopard client versions? (You can indeed run (Snow experimentally) Leopard server on VMware Fusion, currently, as in Parallels...)
Well, I recently wrote a hint here[/url] (great and very helpful site, BTW), but it looks like people had mixed (un)success with this (anyway, completely unofficial and unsupported... and, I would say, probably "semi-legal", as you essentially install a Mac OS X that you own from within your machine, but on another disk, which is only subsequently booted in a "foreign" environment, of which the installer doesn't know anything).
So, hey, Apple, besides this essentially only "academic" hint... what about letting us "power" (or not) users virtualize all your excellent Intel-capable OSes, from Tiger and upwards... ? 
Of course, if Apple changed their licensing terms (IMHO, way too restrictive, and for no reason at all!), VMware could maybe also provide universally-capable Tools for Mac OS X VMs, compatibile both with Tiger - today they crash on a still unsupported Tiger - and (Snow) Leopard, Lion (?), etc.
P.S.: Well, don't take me too seriously: maybe I'm an idealist - but maybe also things could really be better than they currently are...
