Google Sites API version 1.2 includes two new features: “First Web address mappings are now programmatically accessible in API using a new parameter on the site feed: with-mappings=true. Web address mappings enable users to point their own domains to a Google Site to fully customize a site. For e.g., you can map the address http://www.mydomainsite.com to http://sites.google.com/a/domain.com/mysite. Second is Page templates API, you can create templates as well as instantiate new pages from existing templates,” explain Google.
More info: Google Sites API documentation