Most recently Google Sites launched Google Data API which brings tons of new things and more control and usability. Abilities are given,

• Retrieve, create, modify, and delete pages and content.
• Upload/download attachments.
• Review the revision history across a site.
• Display recent user activity.

They also shared the full documentation, Java Developer’s Guide, code samples. Also the announced “We’re also open-sourcing an import/export tool that uploads or creates a local back-up of an entire Google Site.” So, enjoy the new functions and join to developers forum.

via Google Sites: Now with an API!