Stephanie Leary

This plugin applies all content filters to posts and comments and saves them back to the database. This is useful if you have been using Textile or Markdown (for example) and you want to switch to plain HTML.
<h3>Notes</h3>
USE THIS PLUGIN WITH CAUTION. If the results are not what you want, the damage will be irreparable unless you take the following precautions.
You should back up your database first — and be sure that you know how to restore from the backup!
If you are have plugins that allow you to use short codes — e.g. [thing] — you should deactivate them before running this conversion. Otherwise, that markup too will be converted to its HTML equivalent. (The built-in WordPress [gallery] tag should be fine.)
Once your conversion is complete, you should deactivate this plugin and reactivate your short code plugins.

Mass Format Conversion

Applies all content filters to posts and comments and saves them back to the database.

Marzio Carro

Adds categories and tags functionality for your pages.
This plugin addsthe ‘post_tag’ and the ‘category’ taxonomies, which are the names of the existing taxonomies used for tags and categories the Post type ‘page’.
This enables the categories metabox and the tags metabox in the New or Edit Page interface.
The plugin has no settings, does not alter the database and only uses hooks to 
achieve it’s goal. It works perfectly fine with Multisite installations.
This plugin WILL NOT add any display of categories or tags to your template files.
Plugin’s website: <a href="http://technotes.marziocarro.com/category/wordpress-plugins/" rel="nofollow ugc">http://technotes.marziocarro.com/category/wordpress-plugins/</a>
Author’s website: <a href="http://technotes.marziocarro.com/" rel="nofollow ugc">http://technotes.marziocarro.com/</a>

Category Tag Pages

Wonderful functionality

Yes, it works. Uses very few lines of code and it's a simple and safe solution to have categories and tags in pages.

It works

Adds categories and tags functionality for your pages.

Mass Format Conversion vs Category Tag Pages