I installed a new version of Movable Type, which features tags. So, I’ve started tagging my entries. I think the tags are a good addition: they work a bit like categories, but are a lot more specific and thus can be a lot more useful in some situations.
Clicking the tags will show you all entries tagged with the same tag. That’s a not a big list, yet, but I expect to tag all my entries in Autumn, when I’m bored at work… If you click a tag, you’ll also notice that you can subscribe to a RSS feed for a tag, so if there’s a topic you’re particularly interested in — say, TradeResolver — you can grab the feed and get all the new stuff on that topic delivered to you.
I also have a tag cloud (which is the hip thing right now, it seems).