Tag Manager - Tags are crucial for site organization, seo, and for improving user experience.
First-time users need to be able to intuitively find content that is relevant to them. The Tags Page is a start, but isn't very useful for a site with a lot of tags.
I believe the following will all add either improved usability or search engine placement.
1 - Option to limit tags to a list of pre-approved tags.
2 - Any tag not pre-approved is optionally disallowed or goes to moderation
3 - Global edit, delete, search, replace. (e.g. editing a tag changes it in all questions)
4 - Merge tags. (e.g. change 'widget5' to 'widget_5')
5 - Tags page should have a filter just like the tags field on the Ask Question form. This could eventually be replaced by an Advanced Search page.
6 - Admins should be able to remove a tag from a question from either the q-list or q-view without having to edit it. Maybe put an 'x' in the tag span.
7 - Option to wrap tags and add hash symbol in question body. (for styling)
8 - Add tag from answer or comment, as the answer could easily use a tag not in the question. (see #9)
9 - Hash (#) in Q, A, or C)automatically adds tag.