murraypicton

Puts the category and tags of the post in the meta keywords tag in the html to increase SEO compatability. If not tags are found, the full list of tags on the site are used.

Tags To Meta

Increase SEO by putting blog tags and categories into the meta keywords on each page

Timo Schlueter

TagMeta generates meta keywords using your most used tags. 
It automatically gets the 10 most used tags out of your 
blog posts and pages and puts them into a valid meta- 
keyword string. This string then appears in the header of 
the home page of your theme. If you want to add tags per 
post, i suggest youre going to use the Headspace plugin.

TagMeta

TagMeta generates meta keywords using your most used tags.

Tags To Meta vs TagMeta