Version 2.3 of WordPress is due out in about a week. The main new feature is support for tagging. There have for some time been tagging plugins for WordPress, but version 2.3 sees tagging implemented in the core.
Over on my WordPlay blog, I’m running 2.3 beta. After I tagged a couple of posts, it dawned on me that displaying tags requires changing the theme, so change the theme I did.
For a thorough account of adding tagging to your WordPress theme, one that doesn’t assume familiarity with how themes work, see Rich Gilchrest (via Matt).