Google finally released Google Notebook. Google Notebook is a resource provided that allows you to take notes on web sites that you visit. You can mark your notes as private or share them with the rest of the world.
You can compare this to delicio.us, furl, stumbleupon, etc. as a recent way in the past to help increase your web site rankings that would provide links to your web site.
However, because of new developments there is another stronger reason to consider these options. With the Google BigDaddy update, resources point to the development of enhancing searches by what people 'bookmark' and take 'notes' to be a stronger ranking factor than in the past!