The Google AJAX Search API lets you add a dynamic Google search module to your web pages so your users can mash up Google search results with other content on your site or add search results clippings to their own content. Think of it as the Maps API, but for Search -- you just add a single <script> tag to your web page, a few lines of JavaScript, and you have an interactive search box that mixes results from Web Search, Local Search, Video, and Blog Search. Check out the samples and documentation for more information.