Google just announced the official launch of its Google Pages + badges to put on a website or a blog.
All you have to do is to visit this page https://developers.google.com/+/plugins/badge/config and enter your Google+ ID number (you can see it in your URL). This code is clearly for PAGES (even if it works also for personal accounts). If you’re looking to add a +1 button, it’s here.
You can choose from the available gadgets: the big badge (standard) as the one here above and the small badge (with an asynchronous code to insert with HTML5), icons (small-medium-large) and no badge. The choice of “No Badge” offers only one piece of code to insert into the header.
The Google+ Page Badge or icon or even the No Badge is good for SEO : according to Google “the Google+ badge helps you grow your audience on Google+ while also showing more recommendations on Google Search“.