Google added the ability to show popular queries for your Custom Search Engine, so that your users can see what others have been searching for on your site. Popular queries are updated daily, and the code snippet dynamically shows the most recent data.
To show your CSE's popular queries, go to the "My search engines" page (after you've signed in) and click on the "statistics" link. Cut and paste the popular queries code where you would like them to appear on your website. You can also subscribe to the feed for your CSE popular queries using your favorite feed reader -- the link to the feed is also available on the statistics page.