I'm starting to come up with a pretty nice collection of book and reading blogs - not bad, considering I haven't been actively looking for them. Mostly, I just stumble across them while looking for read-alikes for the things I've read or watched. If it looks like the blog is primarily about books/reading, rather than just something with the occasional book/reading post, I add it to my blog list.
Part of me hopes that curious people from those blogs will come visit my own blog after either noticing that I've linked to them (Technorati, Statcounter, and other things can reveal that kind of information) or after noticing that I've commented on their blogs (not likely, since I don't comment often). I think I've managed to attract one or two people through others' blogs - hi there!
Mostly, though, I just like getting a quick look at what other people are writing about. Among other things, looking at book and reading blogs has increased my "to be read" list (not that I need that).