Using Leopard 10.5.7 in VMware Fusion 2.0.4 works great with a little bit of wizardry:

• sudo bash
• cd “/Library/Application Support/VMware Fusion/isoimages”
• mkdir original
• mv darwin.iso tools-key.pub *.sig original
• sed “s/ServerVersion.plist/SystemVersion.plist/g” < original/darwin.iso > darwin.iso
• openssl genrsa -out tools-priv.pem 2048
• openssl rsa -in tools-priv.pem -pubout -out tools-key.pub 
• openssl dgst -sha1 -sign tools-priv.pem < darwin.iso > darwin.iso.sig
• for A in *.iso ; do openssl dgst -sha1 -sign tools-priv.pem < $A > $A.sig ; done
• exit

This basically fixes a bug in Fusion that disables running Leopard Client by changing the required signatures of the ISOs. How nice. I stumbled across this great piece of information here: http://blog.rectalogic.com/2008/08/virtualizing-mac-os-x-leopard-client.html