Generate a preview (aka thumbnail) of any external link in the page, similar to Facebook or Google+ snippets.
This plugin puts the commentor's website screenshot where there is no gravatar.
WordPress Snap is a simple shortcode for display a thumbnail from any website.
Show the Trackbacks Shot
PageGlimpse Bubble integrates PageGlimpse web page previews in your WordPress blog.
Add Snap Shots(TM) to your blog. Snap Shots is an open, extensible platform for creating, sharing, and distributing contextually relevant content.