New AdSense Interactive Ad Spotted
Google constantly experiments with different look-n-feel of their ads to see which one better performs and would generate higher click-through-rates. I've recently spotted an interactive ad (of the size of 300 x 250) which contains a seach box in the middle:
It only advertises one site at a time and allows you to search within the content of the advertised site. Notice that the title of the ad (at the very top bolded) is not a link, rather, mere text. You could navigate through the results by clicking "Next" or "Previous" at the bottom. Here's a screen-capture that illustrates how it works in practice: