Alex Sawallich

This plugins enables the famous Google +1-button in your wordpress-installation. The button is shown beneath 
your posts/pages. With this button you can share the permalink to your post/page in your Google+ profile.
You’ve got the possibility to change the look of the button in the same manner, that you can do by using the 
configurator that Google provides: see <a href="http://www.google.com/webmasters/+1/button/" rel="nofollow ugc">Google plus one</a>.

Google+ One Button

Provides a +1 button from Google+ beneath each post/page.

magnetik

Simply add the google +1 button to sharedaddy.
Please note :
<ul>
<li>Language option is not working at the moment</li>
<li>This plugin is at it’s early stage of developpment. Use just for testing and feedback to : <a href="http://magnetik.org/en/tech/wordpress/english-google-plus-one-1-button-for-sharedaddy-jetpack/" rel="nofollow ugc">http://magnetik.org/en/tech/wordpress/english-google-plus-one-1-button-for-sharedaddy-jetpack/</a></li>
</ul>

Google plus one (+1) button for Sharedaddy (Jetpack)

Add Google plus one (+1) button to Sharedaddy (included in jetpack).

Google+ One Button vs Google plus one (+1) button for Sharedaddy (Jetpack)