This has been added in 2.8! Don’t install this if you have 2.8! Read this instead.
This little plug-in adds a fancy little description field to the “Edit Tag” pane in WordPress. It also adds a function called
single_tag_description(); that does just that but only on the tag page. Not really sure why the tag description isn’t available by default, seems like it would be pretty useful. Basically, you can describe your tags and echo that description on each tag page with the above function; pretty simple!
Please enjoy and note that some of the code came from a thread I read on WordPress.org, but some of it came from extracting similar core code, I just made it into a WordPress plugin. Download it now.