WebThumb is a WordPress plugin by faina09 that creates thumbnails of any web page.
It uses the service at bluga.net where you can register free of charge to have up to 100 thumbnails fetched per month.
Paying a fee this limit can be removed. You can use a shortcode to place the thumbnail images anywhere in your posts or articles.
It is possible to select the size of each thumbnail and some other options. Click on the thumbnail to go to the site.