Google Custom Search Engine
Released on October 24, 2006, Google Custom Search allows anyone to create their own search engine by themselves. Google AdSense results can also be triggered from certain search queries, which would generate revenue for the site owner. This service is currently being beta tested, with bugs, enhancements and feedback from developers being recorded at the "Google Custom Search Engine Enhancement Page".
Google AJAX APIs
Google AJAX APIs is a javascript library to integrate rich, multimedia, search, or feed-based Internet content into web applications/pages, organized by Google. Anyone can utilize them to easily place in rich AJAX content into web pages simply by adding tiny amounts of JavaScript code.
This Library contains many applications which are growing day by day.
Google AJAX Search API
Integrate Google search into a web site