To create Virtual Machines for use with VMWare a VMX Builder is available here.
Instructions on how to convert from scsi to ide disk are posted here.
I'm trying to collect all the free tools and scripts out there to allow manipulation of virtual machines and virtual disks.
Still no idea on what to use as a standard. I think it will be .vmdk for now. For virtual machines it will be VirtualBox. And I'll still have to use VMWare Player and VirtualPC for machines created with these tools. Some operating systems won't run after disk conversion or if run under VirtualBox, although it supports all types of virtual disks above.