ATOI

The main goal we wanted to achieve by writing this plugin was delicate tags appearance tweaking. Now plugin supports tag color and size tweaking, pretty urls, automatic and manual tags and tag cloud output, tag preview and tagged posts count. Such features as tag aliases and search by tag are planned to be implemented in next release.
We are glad to introduce this plugin to the community. If you think that it is necessary and there is need in developing it further, we will do it.
Bug reports and feature requests are welcome.
<h3>Example</h3>
There are 100 posts with tags as your site. 
There are four tags defined: tag1, tag2, tag3, tag4. 
Tag1 has 10 posts, tag2 has 40 posts, tag3 has 20 posts, tag4 has 70 posts (post can have more than one tag). 
There are 3 colors (color1, color2, color3) and 2 sizes defined (10px, 30px). 
So there are 3 color categories and 2 size categories. 
If a tag has less than 33% of tagged posts, it gets into 1st color category. 
If it has more than 33% and less than 66% of tagged posts, in gets into 2nd color category. 
If it has more than 66% of tagged posts, it gets into 3rd color category. 
The same thing with colors. 
So: 
tag1 – 10 posts (10%); color:color1; size:10px; 
tag2 – 40 posts (40%); color:color2; size:10px; 
tag3 – 20 posts (20%); color:color1; size:10px; 
tag4 – 70 posts (70%); color:color3; size:30px;

Xata33 Tag

The main goal we wanted to achieve by writing this plugin was delicate tags appearance tweaking

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.

Xata33 Tag vs Auto Tag Creator