If you are looking for a fairly comprehensive guide to Technorati tags, be prepared for A Consuming Experience.
This is a introductory guide to "tags" on Technorati,
the blogosphere search engine, which started using them in mid-January
2005. It’s a practical introduction rather than a tutorial (ending with
some personal thoughts about tags), but I’ll summarise the basics about
Technorati tags and how to use them in your own blog posts – stuff I’ve
learned from digging around, playing around and, as you’ll see later,
much tearing out of hair. I do assume knowledge of basic HTML (for
which see e.g. this or this), but if anything needs to be made clearer or expanded upon, please post a comment and I’ll try to help.
Even David Sifry, the founder of Technorati, was impressed! Of course, you could always go straight to the source if you want to learn more.