For example, say a website in which I look up 'Thirty Years War,' and it tells me leaders in the field, relevant graduate programs, reigning surveys of the subject, and a bibliography such as the Oxford History of the Thirty Years War.
Not exactly what you're looking for, but depending on what you want, the Cambridge histories might be the way to go. Depending on how recently one was published concerning the field you're looking in to. They always have an agenda that's in step with broad historiographic trends and are almost always written by the leaders in the field. I'm a medievalist and the new Cambridge medieval history is great for that. Otherwise, you might just have to do your legwork. Check out the Journal of Early Modern History and look at the people doing book reviews.