A plugin that redirects you to a post with no tags (or failing that, a random post) so that you can add tags to those old posts of yours.
wz_tagit.phpor it's containing directory to the
Add the following template tag to your website:
I strongly recommend making the template tag in an editor-only viewable area, as the edit link simply won't work for anybody else. Do this by putting the following code in, for example, your sidebar: