Add Meta-Tags to your site, and customize them on a post-by-post basis
A manual meta tag plugin that adds meta keywords and descriptions to pages and posts
Allows forcing users to register and login individually on each post or page.
LogStore is a 'meta' plugin that allows other plugins to log data easily.
Searchable Categories allows a quick real-time search through categories while selecting in new post/edit post view.
Fixes the annoying behaviour of the Facebook share buttons not to show the counter box if something is shared less than 3 times.
Adds a perfect sized version of your post thumbnails for Facebook sharing purposes as well as image_src and og:image meta tags.
This plugin simply adds additional keys to the user meta table upon registration.
Provides random members and/or groups avatar list + blog list with more options /Widget/
Meta Keywords & Description
Allows user to specify All in One SEO Pack details while posting from Windows Live Writer.
A smart plugin that helps you to optimize the blog for SEO purposes.
Simple plugin that put description and keywords for all pages and posts of your blog and clean unnecessary info in wp_head() for secure reasons.
This plugin will remove the generator meta tag from the head of your page.
RSS link for this tag.