I write a lot about Emacs. I also write a fair bit about Drupal. Both are rather geeky topics that may not interest you, or they might be the only things you want to read about. If all the posts you want to read fall into a specific category (example: emacs, drupal, sketches), you go to the category page and subscribe to just that category in your feed reader. If you want to exclude posts in a specific category, here are six ways to filter RSS feeds. Try out http://www.feedrinse.com.
I might occasionally go into firehose-mode, but at least you’ve got a way to control it! =)