ThemeGrill

Allows you to quickly create a maintenance/coming-soon page. You can use this plugin whenever your site is down for maintenance, currently going any upgrade or is in development. Built in options panel to add logo, background image, social icons, color, subscribe field and many more.
Get free support at http://themegrill.com/support-forum/
check the demo at http://themegrill.com/plugins/maintenance-page/
<h3>Features And Options:</h3>
<ul>
<li>Responsive design looks great on your devices.</li>
<li>Logo Upload</li>
<li>Background image/color option</li>
<li>Subscriber Feature to collect emails</li>
<li>Download subscriber list as csv</li>
<li>Social icons</li>
<li>Font Color option</li>
<li>Add title, text message option</li>
<li>Option to exclude page</li>
<li>Custom CSS</li>
</ul>
<h3>Maintenance Page Pro:</h3>
<ul>
<li>Counter</li>
<li>Contact Form</li>
<li>MailChimp integration</li>
<li>Ip Whitelist</li>
<li>Background Slider</li>
<li>Background Video</li>
<li>Progress Bar</li>
<li>Google font option</li>
<li>Analytic Code Option</li>
<li>Role Based access</li>
<li>Font size option</li>
<li>About Page</li>
</ul>
<a href="http://themegrill.com/plugins/maintenance-page-pro/" rel="nofollow ugc">Upgrade to Maintenance Page Pro »</a>
<a href="http://demo.themegrill.com/maintenance-page-pro/" rel="nofollow ugc">View Maintenance Page Pro »</a>

Maintenance Page

Allows you to quickly create a maintenance/coming-soon page. Use this plugin whenever your site is down for maintenance or undergoing development.

Fugu Design

One-click maintenance mode
This plugin adds a button to the admin bar for toggling the builtin maintenance mode.
Core maintenance mode
A .maintenance file is generated and copied to the WordPress installation folder when turning on the maintenance mode. 
A maintenance.php file is generated and added to the wp-content folder for custom HTML code.
Your custom maintenance page will also be active during the core, plugins and themes updates.
<h4>Special Features</h4>
<ul>
<li>
set which roles can switch the maintenance mode
</li>
<li>
set which roles can bypass the maintenance mode on the frontend
</li>
<li>
set the entire HTML code used for the maintenance page
</li>
<li>
preview the maintenance page before saving
</li>
<li>
enable the theme file support, so you can create in each your themes a maintenance.php file to customize the maintenance page
</li>
<li>
restore all default settings
</li>
<li>
restore default HTML code
</li>
<li>
create/delete the maintenance file in the active WP theme
</li>
</ul>
<h3>Translations</h3>
<ul>
<li>English – default, always included</li>
<li>French</li>
</ul>

Maintenance Switch

Customize easily and switch in one-click to (native) maintenance mode from your backend or frontend.

Maintenance Page vs Maintenance Switch