ellbristow

Force all posts by users without Editor or higher role to be private.
This plugin allows you to give your post writers the ability to create and publish posts on your site that are only visible to 
the author, and to editors/admins, by forcing all their posts to be private.
Features:
<ul>
<li>Anyone who does not have the ‘edit_private_posts’ capability can only post private posts</li>
<li>Limit all posts, or only newly added posts</li>
<li>(Optional) Also force a post to have a specific category when posted</li>
<li>Editors, admins and Super admins (who do have the ‘edit_private_posts’) can see all posts, and switch them from private to public if required.</li>
<li>No Configuration!</li>
<li>Just Activate!</li>
</ul>
This is my first publicly released plugin… so I hope you like it. Let me know if you find any bugs!

ForcePrivate

Force all posts by users without Editor or higher role to be private

Soflyy

<h4>Market your content virally on social networks by forcing users to perform a social action before accessing your protected content.</h4>
Check out the 2 minute demo video on YouTube: http://www.youtube.com/watch?v=aheR3_ROt94
Like To Keep Reading is a WordPress plugin that forces visitors to Like you on Facebook to access content on your website.
You can protect entire pages or posts, or just sections of pages or posts (our favorite) – i.e. your visitors can read the first two paragraphs and then must click the Like button to keep reading.
You can force visitors to Like your website homepage, any sub-page/URL on your website, or your Facebook page.
Like To Keep Reading also has optional Google+ and Twitter integration – so instead of Facebook Likes you can get Google +1s and Tweets from your visitors in exchange for access to your content.

Like To Keep Reading

Get more Facebook Likes, Google +1s, and Tweets by forcing users to perform a social action before accessing the rest of your content.

ForcePrivate vs Like To Keep Reading