Blackbam

Create, manage and view snapshots of any post (or custom post type) whenever you want. Like user-managed revisions with a lot of useful functionality.
Features: 
* Create snapshots of any post type including all metadata at any point manually as a secure history and backup of your posts 
* Uses the standard WordPress posts table (like revisions) 
* Uses a custom post status (and therefore works for any post type) 
* Easy snapshot management meta box 
* Create Snapshots comfortably in the publish post box 
* Choose which post types you want to enable the snapshots feature for
PHP Developer API: 
 pos_create_snapshot_from($post_id): Creates a new snapshot for a given post ID 
 pos_delete_snapshot($snap_id): Delete a snapshot by its ID 
 pos_get_latest_snapshot($post_id): Returns the ID of the latest snapshot for a given post ID 
 pos_get_plainview_url($snap_id): Get the URL to the plain snapshot view
This Plugin is sponsored by ready2order GmbH, the company which is producing Austria’s best point-of-sale system. Visit us at https://www.ready2order.com/.
NOTE: The use of a custom post status in WordPress is still in beta. The developers of this plugin are in no possible case responsible for any data loss. 
If you want to be sure nothing happens, backup your database on a regular basis. You should do it anyway.

Post Snapshots

Everything works as expected and I did not hear any compaints yet.

On our live website it has been working great since two months now

Create, manage and view snapshots of any post (or custom post type) whenever you want. Like user-managed revisions with a lot of useful functionality.

sam2kb

This plugin allows any user to add previews of websites right in the content of their posts using a simple [thumb]http://domain.com[/thumb] format. Users may also “optionally” turn on mouseover previews. No purchase or registration is required to use the plugin. Optional upgrade enables PRO features such as “Full-length Captures”, “Free Width Captures” and “Refresh on Demand”.
<ol>
<li>Easily embed website previews in posts</li>
<li>Flexible caching system allows you to store retrieved screenshots on your server</li>
<li>[opt] Display custom images for queued or error thumbshots</li>
<li>[opt] Display thumbshot URLs in a safe manner without linking them directly to the target website</li>
<li>[opt] Display mouseover header preview over thumbshots</li>
<li>[opt] Display mouseover pop-up preview over external links in your posts</li>
<li>[opt] Utilize several Thumbshots.RU PRO features</li>
</ol>
Take a look at Thumbshots.RU for more information (http://www.thumbshots.ru/en/ “Website screenshots provider”).

Thumbshots plugin

This plugin uses the Thumbshots.RU API to replace special tags in posts with website screenshots. Note: This plugin is no longer maintained.

Post Snapshots vs Thumbshots plugin