Here's the presentation on Advanced Custom Search Configuration from Google I/O. You can navigate it with the help of a convenient timeline at YouTube, or download the presentation in PDF format. The talk features Nick Weininger from the Custom Search team on how to create a contextual search experience in minutes, along with details of the Custom Search APIs, including:
- Context and Annotations
 - Advanced features, e.g., Promotions, Synonyms and XML results
 - RESTful URLs for managing Custom Search engines
 - Provisioning API for partners
 - Linked Custom Search
 - Rich snippets and metadata - pagemaps, microformats and RDFa
 - The Blogger search gadget
 - The Custom Search Web Element
 
For more information, please check out the Custom Search developer guide.