Very cool utility on VMware Labs site.
VMware Auto Deploy supports automatic PXE boot and customization of large numbers of ESXi systems. Auto Deploy allows rapid deployment and configuration of a large number of ESXi hosts. After a DHCP server has been set up, Auto Deploy PXE boots machines that are turned on with an ESXi image. Auto Deploy then customizes the ESXi systems using host profiles and other information stored on the managing vCenter Server system. You can set up the environment to use different images and different host profiles for different hosts.