It's an odd thing that it seems to be really hard to find topical blogs to read. There was an article in Forbes, I think, a while ago that listed the Ten Best Sports Blogs and the Ten Best Economic Blogs and things like that, but every so often I get a wild hair and decide, "I'm going to go subscribe to some Science Fiction blogs." So off I go to Google and search for them, and a few minutes turn up blogs by ten or so SciFi writers, but that wasn't quite where I was going. I wanted a blog about Science Fiction. I wanted book reviews, discussions of classic series, thoughts on the physics of Star Trek. Maybe it's different for books. I love to read Arnold Kling, the econ prof, but when you get right down to it, I don't suppose he really produces much other than words, so his blog ought to be good. Anyone who wants to talk about Star Trek probably doesn't output all that much. Same with soccer, Ultimate Frisbee, and a few other things that don't draw many professional writers.
I suppose what it comes down to is that the best blogs are just written by good writers, rather than topical ones. Wouldn't it be cool if you could aggregate blogs by topic rather than by author? Maybe that's the next big thing; of course we don't get topic listings here at blogger. Something to look forward to.