Google offers a new feature that allows users to give a point to some web pages they find interesting.
Clicking on a button will publicly share their point of view on a webpage. This information will be available to friends, contacts and other persons of the web to help them find content that is close to the best of their research.
The principle is quite simple and the official video that introducing the feature is all talk :
Where to start ?
As with any new feature, the first question is: Where do I go to test it? The answer is simple, just visit the site dedicated to the bouton +1 : http://www.google.com/+1/button/
Click on the link Try it now to be redirected on the Google labs. Next, you must click on the button Join the experiment to activate the feature :

Attention, you'll need a Google Account to use the feature.
Congratulation, You can now use Google +1:

Make a search on google.com (the feature is not availabler on specific country Google sites). The button Google +1 will appear next to search results :

When you first click a Google +1 button, a popup will ask you to confirm the creation of a profile and how you want to appear :

When you have marked a page with the Google +1 button, it's color change to blue :

You can have a list of all link for which you mark Google +1 directly from your Google profile page :

Google +1 in web pages
The goal is to display a Google +1 button on web pages and users could see who from their friends have marked the page. The user can also click on a Google +1 button without leaving the site. This last feature appears clearly essential to the success of Google. +1.
You can register to receive updates on the implementation of this feature from this form: https://services.google.com/fb/forms/plusonesignup/
Following my subscription, I recently receive a mail from Google inviting me to integrate the button on my website: http://www.google.com/webmasters/+1/button You will see that you can customize the button size and the language to display. The code to insert is quite simple, there is two lines. The first one is to call the JS from Google and the second is to render the button:

I could implement it on my blog (http://hugon.ws) in less than 5 minutes:

The tools for Google +1
Again, who said new feature, also talks about new tools to use it.
An extension for Google Chrome is apparently expected since we can see a preview in the promotional video titled "Dear Sophie" :
You'll notice in the toolbar for Google Chrome the presence of a Google +1 icon. We can easily imagine that eventually, other browsers also offer a similar extension. It also intends to speak with insistence of an integration of Google +1 within Google Analytics to monitor data from the pages of websites.
References
The official site Google +1
The Google +1 FAQ
Google +1 your website
The official Google blog
Keep in touch with news from Google +1 for web site
Informations about the extension Google +1 for Google Chrome
Informations about the integration of Google +1 into Google Analytics