In the past week, Google have updated their search results to show an instant preview of a website on the right hand side of the page as shown below.
These are activated by simply selecting the magnifying glass next to the search result. By default they are not shown. This is another welcome addition by the team at Google, who have been making quite a few changes recently along with Google Instant, which allows the user to see their results as they type; and changes to Google Places, which you can find out more about here.
Bing have had a similar feature for a while now with their "more about this site" option, but it will be interesting to see how they react with all the big changes happening at Google.
Have fun searching!