It should come to no surprise to anyone that I am a fan of del.icio.us, Flickr, and Technorati. And, it should be equally un-shocking that one of my favorite aspects of each of their services is Tagging, the practice that begat the concept of Folksonomy. So, when Six Apart released a tagging plugin for Movable Type, I was excited. Alas... alas, though, to add the tagging functionality, you had to override the "Keywords" field in your entry creation page. That's no good. The system already uses the Keyword field so a user can override the entry's URL normally constructed by the title text.
So, I rolled my own. Blog@Case now has tagging! When you are creating an entry, you should see the "Tagging" text field right below the "Keywords" field. (If you don't see it, on that same create-an-entry page, look for a link below all the text fields called "Customize the Display of this Page" and make sure the Keywords field is one of the fields being displayed.) The relevant documentation is in the FAQ. Basically, it works just like how they described Six Apart's tagging plugin except that it doesn't override the Keywords field. So, all of their documentation is, basically, accurate.
So, go ahead and get taggin'.