Have you signed up on Blogher yet? I think they have categories there.
Is it possible to search on Blogger?
The only way I know is to add what things interest you in your profile under interests, books, etc. Then click on them and they will show you other people who have the same words on their profiles. It isn't the best way in my opinion, but it seems to be the only option blogger gives us. If you find something easier, let me know.
I would find blogs I liked, and check out their blogroll list, and add those, and so on. =)Sometimes if you just google stuff, you find peoples blogs.