This plugin will convert every word that occurs in a post title or content into a term (tag). By default the plugin will add these terms to a new taxonomy called “words”. Optionally, the terms can be added to the “post_tags” taxonomy, used for normal tagging in WordPress.
The plugin provides the option to create a so-called stop list. Words in this list will be kept (or even removed) from the taxonomy. This allows authors to ignore meaningless, but often occuring, words like ‘a’ or ‘the’.
This plugin makes sure that the tags will actually cover a blog’s content. This is great in combination with tag-clouds as the tag-clouds will better show what the blog is about.

Text2Tag

This plugin automatically converts title and post contents to tags.

WPGurus

Important: This plugin works with every theme that uses the recommended WP function for displaying the title. For other themes, that display the title using a lesser know method, it might not work.
This plugin adds a simple metabox beside the post creation form in the WordPress admin interface, allowing you to toggle the visibility of the title. Unlike some of the other similar plugins available in the WordPress repository, it completely removes the title instead of just hiding with CSS or JavaScript.
Some advantages of using this plugin:
Does not affect menus or the admin area: Before removing the title it checks to make sure that the front-end is being displayed and the current point is within the loop. In other words it has no effect on menus or post tables in the admin area.
Works with all post types: To hide the title you just have to use a checkbox on the post creation form. This checkbox is displayed in the form of a metabox for all post types.

Title Remover

Gives you the ability to hide the title of any post, page or custom post type item without affecting menus or titles in the admin area.

Text2Tag vs Title Remover