Technorati

Technorati is a search engine for blogs. you can search blogs and tags and it ranks blogs from around the world.
Its different from google because it searches only in blogs instead of every type of website. when signed in, other peoples blogs can be read without going onto it like an rss feed.
Technorati gives you a rank and authority which are measured by the blogs popularity, how old it is, how many other people link to it, etc. Right now, my rank is 815,820 and my authority is 6.