I just started creating my categories for my Tool Reviews site (Power Tools, Hand Tools, Lawn and Garden Tools, etc) and discovered that you can create sub-=categories off of a parent category. Now that’s cool (and something I haven’t encountered in the other blogging tools I’ve tried - blogger, movabletype (update: MT 3 has subcategories), and typepad). And I’m sure it makes things even better for the search engines to figure out what you’re writing about.