Technorati: Not just a site.
This is a great place to find interesting blogs...I like how it is organizes by category, arts...music...entertainment...etc. When I did the searches on Learning 2.0 the results were very different. With the "blog directory" search I found some PLCMCers right away with there being only 9 hits! On the other end of the spectrum, there were over 28,000 when searching in blog posts, which makes sense since it is searching all the posts. I think that I would use Technorati if I wanted to find a blog on a certain subject. It also helps you find what's hip out there in the blogosphere...like Boing Boing.