This SDN article demonstrates the two useful commands: amadmin and psadmin. Together, these commands can automate practically any task related to portal administration. The article uses a step-by-step example for creating a new organization with a portal based on the Enterprise Sample. Source code is included and there are bonus files that also create a new organization based on the Developer Sample.
If you were wondering how to migrate a portal from one environment to another or script your customized portal deployment for developers then this article provides valuable information.