Check out DCBlogs (it’s now linked in the right column under “News Aggregators”). Blogs are listed here by in 24–YES, 24–different categories. Here’s a blurb about DCBlogs the FAQ section from the editors:
The main dcblogs.com page is a news site. It reports on topics raised by bloggers, changes in the DC blogging community, as well as bring new blogs to the attention of readers. We’re always on the hunt for interesting content and suggestions are encouraged — let us know about your work or the work of other writers that you think we should be making a note of. Just write [email protected] If you would like to join the ranks of regular contributors.