Brian Zeligson

WP Custom Taglines adds a meta box to your posts and pages with two options, Enable Custom Tagline, and Custom Tagline Content. Checking 
“Enable Custom Tagline” will cause your site to display the contents of the “Custom Tagline Contents” field on your site when that post or 
page is viewed, instead of the sitewide tagline.
Check out http://www.workinginboxershorts.com for more plugins, for support or questions, or to contribute code.

Custom Taglines

WP Custom Taglines allows you to specify a custom tagline for each post or page that will override the sitewide tagline for that post or page.

mattyboy

Tagline History plugin detects when you change your tagline and keeps track of all the changes that you make. These changes can then be output onto a page of your choice for your users to look over.
Features
<ul>
<li>Customizable template and style sheet for Tag History list.</li>
<li>Customizable date format.</li>
</ul>
This is my first attempt at creating a WordPress plugin and I welcome any feedback or comments about it.

Tagline History

Tagline History stores your tagline changes and display a history of taglines to your users.

Custom Taglines vs Tagline History