Thomas Schulte

This plugin dynamically shows preview screenshots of hyperlinks as tooltips on your WordPress site.
For the tooltip effect a jQuery plugin called “qTip2” is used internally. 
Find more about this great project here: http://qtip2.com/ 
The thumbnails are provided by http://thumbsniper.com and its API.

ThumbSniper

This plugin dynamically shows preview screenshots of hyperlinks as tooltips on your WordPress site.

Robo

WP-Thumbnail is a simple and neat WordPress Plugin that not only allows you to use a short-code to generate dynamic 
screenshot of webpages in your posts but also takes a realtime snapshot of the served webpage and saves a link to it 
on the page itself that too without burdening the servers. This helps in optimizing search results on Google by adding 
a thumbnail to the left of the search result snippet and makes shared posts more attractive, with a relevant thumbnails, 
on Social Sites like Facebook.
For more information, check out <a href="http://wp-thumbnail.robocasters.com/" rel="nofollow ugc">wp-thumbnail.robocasters.com</a>.
Features include:
<ul>
<li>Short-Code – The plugin has a shortcode that enables you to add dynamic screenshots of webpages to your post.</li>
<li>Meta Thumbnail – It uses meta name thumbnail and adds the live screenshot in it for being displayed as a thumbnail in Google Searches.</li>
<li>PageMaps – PageMaps is a structured data format that provides Google with information about the data on a page. It enables website creators to embed data and notes in webpages.</li>
<li>Facebook OG:Image – It sets image with content og:image to the top priority for being used as a Facebook Post thumbnail.</li>
<li>WP-Thumbnail Class – It adds a WP-Thumbnail class that helps image to be used for all other sharing purposes.</li>
</ul>

WP-Thumbnail

'Changing the way you share', giving you an experience you have never had before...

ThumbSniper vs WP-Thumbnail