see this document, it may be a good starting point
http://communities.vmware.com/docs/DOC-4210
Q: How do I create a VM?
A: New virtual machine can be created using New-VM cmdlet. Before, executing this cmdlet first you need to connect to server. Below script would create a new virtual machine in the same host.
New-VM -Name "Target-VM" -Host (Get-VMHost)
Also, there is some great stuff in the vSphere™ PowerCLI Forums