WordPress.org

Linking relevant words internally to your tags provide benefits both from a search engine optimization point of view as well as giving relevant context for users wanting to explore your site. When starting a new site, you might not have a lot of tags in your archive yet, and you don't want to go through your old posts adding new relevant links each time you write a new article.

This WordPress shortcode adds a link to a specified tag, but -only if it exists-. Otherwise the text in the shortcode is shown just as usual. You can also specify several tags separated with semicolons, and let the plugin check if any of them exists.

Usage: [taglink tag="tag1;tag2;..."]text[/taglink]

For instance: [taglink tag="css;web development;technology"]stylesheets[/taglink]

will output

<a href="http://yourdomain.com/tag/css">stylesheets</a> or 
<a href="http://yourdomain.com/tag/web-development">stylesheets</a> or 
<a href="http://yourdomain.com/tag/technology">stylesheets</a> or
stylesheets

depending on which (if any) tag exists. If no tag is specified, the content ("stylesheets" above) is assumed as the tag.

Read more at Jacob Rask, the plugin author's site.