Sanbarrow has done a great job of documenting the VMX file.
My favorite tips are
Have a look in :
C:Program FilesVMwareVMware Playerlinux.iso
Xen Hardware Compatibility List (HCL)
There is an OpenVZ live-CD VZ VM server with VZ VM guests (based on CentOS or KNOPPIX) that you can download from http://wiki.openvz.org/Download_live_CD
And there is a quick start guide to read at http://wiki.openvz.org/Getting_started_with_OpenVZ_live_CD