If you are viewing the entire blog ("all" option on the menu) then you have the option to subscribe to "all posts" or "all comments". But if you are viewing one of the section pages, you also have the choice to subscribe to just the posts in that section. This means that if you visit the Theatre of Noise only to read about photography, you can limit your subscription to photography posts. Of course, this means that you will miss things like this very announcement you are currently reading, so maybe also subscribe to the entire site and give it a lower priority in your reading schedule.
One issue I am facing is that readers don't get any of these options when viewing an individual article. There seems to be no way to write code conditional on the category a post belongs to. Or rather, I am sure there is some way to do this, but extensive hacks like this are undocumented in Blogger land. Do you have a solution? Please comment below!
As a final change, I discovered that a good dozen of my more recent posts were not showing up under any section heading. I don't know where their tags went, but they are now all present and accounted for!