P. Chandra

Automatically adds a META keywords tags with keywords within the html HEAD tags. The categories are used as keywords. 
Note: Works on single posts only as they are assigned categories.

Quick META Keywords

Automatically adds a META keywords tags with keywords within the html HEAD tags. The categories are used as keywords.

GB071

ecreateinfotech

This plugin automatically converts keywords in a post/product title and category to tags upon saving. It includes a user-editable list of words you want the plugin to ignore
<ul>
<li>Converts keywords in post/product titles to tags</li>
<li>Converts keywords in post/product category to tags</li>
<li>Includes user-editable list of words to be ignored</li>
<li>Setting to enable for title and category separately</li>
<li>Setting to overwrite previous tag and consider only title and category while generating new one</li>
<li>Converts on publish and update.</li>
</ul>
Multi-blog adminstrators take note: this plugin is especially helpful if you’re building a community-based site where tagging is important and your bloggers are not always diligent about tagging.

Auto Tag Creator

Automatically creates tags from post/product title and category, on update or publish.

Quick META Keywords vs Auto Tag Creator