WP-Colophon gives you the ability to add a Digital Colophon into the unobtrusive WEB_AUTHOR meta tag.
In my quest to find a dead simple solution, I came across two other meta tag generators. This plugin takes the best of both plugins mentioned below and makes a dead simple plugin where web developers and designers can leave their company name / authorship info in the WEB_AUTHOR meta tag.
Head Meta Data - Head Meta Data adds a complete set of tags to the section of all posts & pages. - http://wordpress.org/plugins/head-meta-data/
Simple Meta Tags - Allows you to set global meta tags and customize on each individual page/post. - http://wordpress.org/plugins/simple-meta-tags/