by Dougal Campbell on WordPress.org
Automatically add <link>, <meta> description and <meta> keywords to your HTML on a per-post (or page) basis.
HeadMeta creates “description” or “keywords” tags for individual
posts or pages. It can also create arbitrary or tags.
These are easily set on a per-post (or page) basis by simply adding Custom
Fields.
See the Installation section for more detailed examples.