Technorati have launched a service so that you can search for blogs on a specific topic using blog-level tags (initially scraped from your categories). I’ve been wanting this for ages, so that I can at last go and find ‘blogs about copyright‘ rather than ‘posts about copyright‘ or ‘posts that happen to mention the word copyright, probably at the bottom of the page instead of using a ©‘.
Go, claim your blog and add in your blogtags.