If you're just looking to embed a standard google search in the page (i.e., user types in search terms and they get displayed on a result page), I believe the Google AJAX Search API should provide what you need.

If, OTOH, you want to programmatically submit a search behind the scenes and do processing of the returned results before (or instead of) displaying them on a web page for the user, then, so far as I've been able to determine, the only option for doing so at this time is to violate google's terms of service.