robpannell

From the plugin admin screen you can create rules by specifying a key word or phrase along with an existing 
WordPress category. Th plugin then scans post titles for the key, and adds the specified categories as appropriate. 
By default the plugin will automatically check newly created posts when a page is loaded, however this can be set to manual via a button in the admin screen.
I can’t guarantee any support, but if you use the support forum I will do my best to help you with any issues. 
Feel free to suggest improvements too.

Smart Categories

This simple plugin adds categories to posts based on key words or phrases in the title.

webvitaly

<ul>
<li><a href="http://web-profile.net/wordpress/plugins/taxonomy-checklist-tree/" title="Taxonomy Checklist Tree" rel="nofollow ugc">Taxonomy Checklist Tree</a></li>
<li><a href="http://web-profile.net/donate/" title="Donate" rel="nofollow ugc">Donate</a></li>
<li><a href="http://web-profile.net/wordpress/plugins/" title="WordPress plugins" rel="nofollow ugc">WordPress plugins</a></li>
</ul>

Taxonomy Checklist Tree

Plugin sets Category/Taxonomy checklist hierarchical tree-view by default.

Smart Categories vs Taxonomy Checklist Tree