In the beginning, there was the Google (SOAP) Search API. In December 2006, Google no longer issued any new keys for this API. Those with keys already could still use the API, but it was effectively deprecated.
Yahoo has announced some new updates to SearchMonkey its relatively new platform that allows web sites and web content publishers to format and custom search results on Yahoo search pages. The new updates include additional content types that can be included in search results and support for Google Base formatting for structured data feeds (our Google Base API Profile).