OK, just abusing my blog for shameless bookmarking purposes:

http://blog.rectalogic.com/2008/08/virtualizing-mac-os-x-leopard-client.html

Background:

As of 2.0 beta2, VMWare Fusion supports OSX Server as a guest OS. OSX Client will cut off during the install, saying it’s not OSX Server (ORLY? YARLY!).

The link provides info on how to install OSX Client in VMWare. I prefer the sed/resigning trick.