Stefan Goßner has put together a terrific 4-part series on the SharePoint Content and Deployment API here.  It offers a great overview and very good examples in code (C#). 

I first picked up this link from joris poelmans blog at http://jopx.blogspot.com/.

Even if you’re like me, in that you have not had to do much hands-on work for content management, this is well worth 20 minutes of your time to read. 

Using the API, one can:

• Export and import content very easily.
• Re-parent content.  If you want to export some content from a site "A" and send it to site "B" but in a totally new place in the hierarchy, this is possible.
• Export content from a site A and import selected bits into site A.
• Re-link content (meaning deal with all the hyperlinks).