WebSnapr lets you capture screenshots/thumbnails of almost any web page. Let your visitors to instantly visualize any web page before clicking. WebSnapr also provides us the WebSnapr Preview Bubble which is a simple, unobtrusive script used to display an overlay bubble showing a hyperlink target thumbnail using WebSnapr. It’s a snap to setup which can increase site traffic, click-through rate and site stickiness.
Currently 289800028 site thumbnails served and counting. You also be able to display the images of previewed website as del.icio.us does.