Last week I wrote about creating my following page and a related OPML file which one could put into a feed reader to subscribe to the list itself instead of importing it. I haven’t heard anyone mention it (yet), but I suspect that like I, some may be disappointed that some feed readers that allow OPML subscriptions don’t always respect the categorizations within the file and instead lump all of the feeds into one massive list. Fortunately there’s a quick remedy!
WordPress in its wisdom used a somewhat self-documenting API that allows one to create standalone OPML files by category. Thus if you only want to subscribe to just the feeds categorized as IndieWeb related in my OPML file, you can append the category id to the end of the URL to filter the others out.
The main OPML file: http://boffosocko.com/wp-links-opml.php
The IndieWeb only file: http://boffosocko.com/wp-links-opml.php?link_cat=1521
So in general, for WordPress sites one can append ?link_cat=[category id] (with or with out the brackets) to the main URL for the OPML file typically found at http://www.example.com/wp-links-opml.php.
I was going to post about this later this week after running across it this weekend, but by odd serendipity, while I was subscribing to Henrik Carlsson’s site I noticed that he posted a note about this very same thing recently! Thanks for the unintended nudge Henrik!
For quick reference, below are links to the specific OPML files for the following categories within my larger OPML file for those who’d like to subscribe to subsections:

Bloggers
Entertainment Industry
Higher Education
Indieweb
IndieWeb and Education
Information Theory
ITBio
ITBio Related Conferences & Workshops
ITBio Related Research Groups
Mathematics
News
Open Education
Podcasts
Sampling