Better Tags Manager (BTM) allows you to edit tags from the manage post section without having to visit the post itself.
In addition to that it will allow you to filter out posts which do not have tags and edit or bulk edit them. If you do not want to edit tags individually you can filter out and edit bulk posts at once by choosing the bulk edit option.
A nice little feature with the plugin is that it will also allow you to add tags to multiple posts without having to edit a single post. So say you want to tag all posts with â€œchickenâ€ in it as â€œBirdsâ€ simply use the search option and search for chicken.
Check out here for the plugin release page Better Tags Manager Release Page