Tag Posts Widget is a light widget to show posts from a given set of tag.
Ispired by Category Posts Widget by James Lao – http://jameslao.com
Features:
<ul>
<li>Select any number of tag to be shown.</li>
<li>Add the tag browsed, while browsing the tag archives.</li>
<li>Set how many posts to show.</li>
<li>Option to append the tag names to the title.</li>
<li>Multiple widgets.</li>
</ul>

Tag Posts Widget

Adds a widget that shows the post from a given set of tags.

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.

Tag Posts Widget vs Auto Tag Creator