Back in 2006, Google had a product named related links, which showed related sites on the internet based on your content. Google just recently relaunched related links at relatedlinks.googlelabs.com. The major difference between the old related links and the new one is that the new one only shows related content from within your site, whereas the old one took away visitors from your site.
Often, Google Related Links were confused with AdSense. They did and do look somewhat similar to AdSense link units.
The new related links can be tried out over here. Here is a picture of how they may look:
Back in the day, Yahoo had a product that was somewhat similar named YQ. YQ is no longer active at this point.
Hat tip to both Google Operating System and Google Blogoscoped.
Related Topics: Google: Web Search
Search and discovery / recommendations are so closely connected, it seem inevitable that Google would want to cover both. Case in point: the description of the new music search in the Google blog notes “a search engine should also be able to help you discover music you’ll like.” http://bit.ly/2d8Uwt