Google Related Links is a new Labs service that help webmasters increase page views on their sites. Given a page on your site, Related Links can choose most related pages from your site and show them in a gadget. You can embed this gadget in your page to help your users reach other pages easily. Related Links also suggests searches that users can run within your site to find even more related pages. The service is currently ‘invitation only’ apply email@example.com (stating your Gmail address, website domains and approximate pageviews per day). Once you get invitation, login using your Google account and click on "Manage Related Links". You'll be able to configure gadget, customize look & feel and enable some advanced features: highlighting keywords from page for visitors that come from a search engine, blacklisting web pages from list of related links and removing prefixes or suffixes from titles. After configuring gadget, paste the code in your site.
Source:→ Google OS