One year ago Google launched their GoogleBuzz button which allows people to share links and interesting stuff with others. While it had a good start, it was not very successful as expected because people are more connected with facebook and therefore use facebook like and share rather than GoogleBuzz.
Crossride led the idea of Google search+Facebook share, one step further by creating their cross browser browser plugin, Google + Like that adds the facebook like button in every Google search result.
It seems a simple idea in principle but can be quite useful to help you decide which search result to visit based on what your friends have recommended.
This plugin does not slow down the search process because it loads after return of search results.
You can download it for free here