Technorati.com

This blog search engine now searches for social media too —photos, video and music posted on online sharing sites — and a tag cloud on the home page shows you the hot topics of the day. Blogs are given an authority rating, based on how many other blogs currently link to it. The new BlogStorm also tracks blog love; register your site to receive free statistics. Another honorable mention goes to Sphere, where you can select a topic (Sports, Politics, Entertainment) and the site will generate links to the most popular blog posts, news stories and other related content.