Anthony

This plugin will limit access to the site. Only visitors with a cookie token will be able to access the public website. Visitors without the cookie will see a “coming soon” style of page.
You can customise the “coming soon” content, and you can change the way tokens work. Visit yoursite.com/?add_token to receive the token allowing you to see the site. To remove the limited access, simply disable this plugin.
By default, the token is “letmein”. So use these links: 
site.com?letmein 
site.com?takemeoff
This plugin is useful when you’re developing your site. You can work on your live web server without having your site open to the public.

Token Access

Limit access to the site to those with a cookie token.  Visitors without the cookie see a customisable "coming soon" style of page.

Nagmay

Let anonymous users preview a post before it is published!
Have you ever been writing a post that needs to be reviewed by someone who does not have access to log in? This plugin generates a simple URL that can be given out for public preview.
Based on Public Post Preview 1.3 by Matt Martz and Jonathan Dingman. Unlike Public Post Preview, the Simple Preview can be accessed by more then one user. The 24hr time limit has also been removed.
<h3>Upgrading</h3>
<ol>
<li>Click update from the WordPress plugin menu.</li>
</ol>
or
<ol>
<li>
Click ‘Download’ on this page.
</li>
<li>
Deactivate the simple preview plugin through the Plugins menu in WordPress Admin.
</li>
<li>
Upload the folder to your /wp-content/plugins directory, overwriting the previous version.
</li>
</ol>

Simple Preview

Let anonymous users preview a post before it is published!

Token Access vs Simple Preview