First lets dive into the definition of a governance plan infact more importantly what will it do for your enterprise. MOSS/Sharepoint is a collaboration platform and when the process of collaboration begins after deployment many processes will be required to maintain the integrity of data and structure within the enterprise portal.
- Team Structure & Responsibilities: Business Owners, IT Admin, IT Support
- Operational policies: System Admin, Portal Admin, Extranet Maintenace(optional)
Quoting from the Document: "The SharePoint Governance Plan is a guidebook outlining the administration, maintenance, and support of X Corporation’s SharePoint environments. It identifies lines of ownership for both business and technical teams, defining who is responsible for what areas of the system. Furthermore it establishes rules for appropriate usage of the SharePoint environments"
Please refer to the link below which provides you with a comprehensive template to create your own Governance plan for your enterprise.
You will find many other useful resources on the technet site.