Just checked out Iterend (http://blogs.iterend.com/en/), a new search engine (currently) focussing on Blogs. They're still in private beta, and it looks like their index is not quite that large, but I found what was retrieved by my sample searches to be relevant. They also have the standard tag cloud, as well as categories for the blogs. Of particular interest to reputation and media monitoring companies is the API, which allows you to integrate Iterend's results into a custom application.
If they can make sure their final index is not full of duplicate and spammy entries, they'll have a nice contender for blog search.