sammychen

This plugin will automatic add links to technorati tags or your blog’s tags where the words in your post match the tags of that post.
The most greatest things is that the plugin will not actually change your posts’ content in order to add links, so it will not hurt your posts. If you don’t want to use this plugin, just deactive it, and all links the plugin generated will automatic disapper just like they automatic come out, then your blog will return to its original status.
Go to Settings->Tag to Link for more information.
Rules Of Match 
Here are some rules when and how the convert take actions. These rules are only effective after version 0.5
<ol>
<li>If you tagged a post ‘hello world’ ‘hello’ ‘world’ and the content of your post is ‘hello world, I’m coming’, then this plugin will add link to ‘hello’, ‘world’, but not ‘hello world’, because there are links already. The rule can be simplily called Short Tag First.</li>
<li>If you tagged a post ‘hello world’ ‘hello’ ‘world’ and the content of your post is ‘bigworld, hellod, world’, then this plugin will add link to the last ‘world’, and no links will be added to ‘world’ of ‘bigworld’, or ‘hello’ of ‘hellod’.</li>
</ol>

Automatic Tag Link

This plugin will automatic add tag links to words in your content match the tag.

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.

Automatic Tag Link vs Auto-tags