microkid

This plugin gives you full control over the permalinks for author pages. When using “pretty permalinks”, by default URLs to author pages are structured:
http://www.example.com/author/author-name/
With this plugin you can change the “author” part of these URLs into anything you like, for example:
http://www.example.com/editorial/author-name/ 
http://www.example.com/crew/author-name/ 
http://www.example.com/members/author-name/ 
http://www.example.com/posts-by/author-name/
The plugin will also automatically change links throughout your site that point to author pages. The URLs of author feeds are also changed.
Visit the <a href="http://www.microkid.net/wordpress/author-slug/" title="Wordpress Plugin: Author Slug" rel="nofollow ugc">plugin’s homepage</a> if you have any comments questions.

Custom Author URL

Customize the author slug in the permalink for author pages.

Grégory Viguier

With this plugin, administrators can change the default author base in the registered users profile url, and the author slug of each user. 
Changing an author slug is a good thing for security (if your login is “This Is Me”, your slug will be “this-is-me”, a bit easy to guess). 
The plugin adds 2 fields for this purpose, one in permalinks settings, the other in a user profile.
<ul>
<li>Default: example.com/author_base/author_nicename/</li>
<li>Customized: example.com/jedi/obiwan/</li>
</ul>
<h4>How to edit the slugs</h4>
<ul>
<li>Go to Settings > Permalinks to edit the author base: “author” => “jedi”</li>
<li>Go to Users > “Any user profile” to edit the user slug: “agent-smith” => “obiwan”</li>
</ul>
<h4>Translations</h4>
<ul>
<li>English</li>
<li>French</li>
<li>German by <a href="https://wordpress.org/support/profile/carny88" rel="ugc">Carny88</a></li>
<li>Spanish by <a href="https://wordpress.org/support/profile/oliverbar" rel="ugc">Oliver</a></li>
</ul>
<h4>Multisite</h4>
<ul>
<li>The plugin is ready for Multisite.</li>
</ul>

SF Author Url Control

Allows administrators or capable users to change the users profile url.

Custom Author URL vs SF Author Url Control