When you register your blog with Technorati, you must choose 1-3 preselected categories to describe it.
There are special categories for "Anime" and "Hockey" but none for "History" or "Biography" or even a vague "Social Sciences." Or for that matter, "Education." My blog is pure history/biography. I wound up choosing "Home" (I do talk about Thomas Jefferson's home life and sneak in a recipe now and then), U.S. Politics" (even though this is completely about the years after he retired from politics), and "Celeb" (even though most people would understand that to mean gossip about living or recently dead celebrities, rather than serious biography about founding fathers).