Show how many posts are tagged with a tag?

Is there a plugin that will display, on the post editor, how many posts each tag has been applied to?

So when enter a tag into the tag field on the post editor, and it displays the matching tags, it also displays how many posts each of those tags has been used in e.g.

themes (1)
wordpress themes (4)

That way I can avoid using lesser used tags to tag a post.

Thanks!