Bartosz Romanowski

This plugin provides a simple [tag] shortcode.
Replacing patterns:
[tag]tag name[/tag]
<a href=”http://yourdomain.com/tag/tag-name/” title=”tag name”>tag name</a>
[tag slug=”tag-name”]your text[/tag]
<a href=”http://yourdomain.com/tag/tag-name/” title=”tag name”>your text</a>
[tag name=”tag name”]your text[/tag]
<a href=”http://yourdomain.com/tag/tag-name/” title=”tag name”>your text</a>

Simple Tag Shortcode

This plugin provides a simple [tag] shortcode.

jfoucher

This plugin uses the yahoo.com API to find the most relevant keywords from the content of your post, and then adds them as tags.
The tagging is fully automatic, so if you’re using a plugin like feedwordpress to display RSS feeds on your blog as posts, everything will get done as the feed posts are published. No user intervention necessary!

Auto-tags

Automatically add relevant tags to new posts.

Simple Tag Shortcode vs Auto-tags