Michael Arrington of TechCrunch has written a review of Sphere – a new blog search engine which, he says

quite frankly blows everything, and I mean everything, I’ve seen out of the water in terms of relevance (and, by the way, design…Adaptive Path was involved).

Sphere’s search tackles the thorny issue of relevance by having

an analysis of links into and out of a blog, an analysis of metadata around a post (links, post frequency, length of posts, etc.), and something Tony calls their “secret sauce�, which is content semantic analysis to filter out spam and to understand what a blog post is talking about.

The results

show only two posts per blog on the first page, so no one blog can dominate a category. The result set has auto-generated profiles of blogs that include recent links in and out of the blog, average posts per week, average words per post and a link to a full page profile that can be edited by the blog author.

Sphere has apparently been indexing blogs since January 2003 so you would imagine they have a fairly comprehensive database to start from!

You can sign up for a beta of Sphere here and see the screenshot Michael put up here.