I had a bit of difficulty implementing categories fully. The sticking point had to do with changing the footer on my entries to contain the category name and link to that category's archive page, as well as adding a list of categories to my main archive page. The MT user manual does give you all the information you need, but it's in bits and pieces all over the place. A few examples would have helped me immensely.
Normally, I'd simply view source on someone else's blog to guide me, but MT renders all of its tags in index files, so what you see when you view source is the finished product. That's not helpful, since I want to see the code. I figure someone else might benefit from this, so I've documented everything I did and placed it in this text file here. It's in a text file to ensure that MT doesn't try to render its tags, and to make it easier for anyone interested to save a copy for themselves. I may update this file someday as I dink with my blog config, so I'll add a link to this file in my main index under Blog Resources.
UPDATE: Byron found this post useful, and he's added some corrections for those who've updated to MT version 2.64. He's also made me realize that I don't have categories configured for my individual archives, a situation I'm about to rectify.Posted by Charles Kuffner on July 27, 2002 to Administrivia