Site Explorer Beta is open for public:
Why is this search different?
Site Explorer allows you to explore all the web pages indexed by Yahoo! Search. View the most popular pages from any site, dive into a comprehensive site map, and find pages that link to that site or any page.
Now if someone can explain me how to view the most popular pages from my site, please do! Furthermore I’m a little underwhelmed, because I’m not sure what this form of search could be usefull for.