Google's likes +1 button.

Sometimes it’s easier to find exactly what you’re looking for when someone you know already found it. Get recommendations for the things that interest you, right when you want them, in your search results.  

About the +1 button 

Use the +1 button to publicly show what you like, agree with, or recommend on the web. The +1 button can appear in a variety of places, both on Google and on sites across the web. For example, you might see a +1 button for a Google search result, Google ad, or next to an article you're reading on your favorite news site. Your +1’s and your social connections also help improve the content you see in Google Search. Learn how to +1.
  

What happens when you +1 something?

When you +1 something, the +1 button will turn blue and the +1 will be added to the +1's tab  of your profile. Here you can manage all your +1’s and decide whether you want to publicly display the +1’s tab. 

Regardless of whether you chose to publicly share your +1’s tab, your +1’s will still be visible to others viewing the content you +1’d. For instance, your +1 could appear as part of an anonymous aggregated count of the people who have also +1’d the same thing. Your name could also appear next to the +1 to help your friends and contacts identify which content may be most useful to them.

Control who sees your +1's

You can control the visibility of the +1’s tab on your profile. However, remember that +1’ing is a public action. Anyone could potentially see items you’ve +1’d when they visit the same places on the Web.

For example, imagine two women--Arielle and Kyla--who've never met. Arielle, an architect, decides to +1 her favorite design website. Kyla finds the same site on Google Search and sees Arielle's +1, even though she doesn't know Arielle. Arielle's +1 helps Kyla decide to check out the site, and Kyla ends up loving it!