Brian Messenlehner

Display a Google+ Direct Connect Badge on your site via widget or shortcode, allow your members to login/register via their Google+ account or sync your Google+ stream with your blog posts or BuddyPress activity via the Google+ API.
WordPress Google+ Connect allow your website members the ability to register and/or log in via their Google+ account utilizing the Google+ API. Set up a Google Plus Application and store the API credentials in the WordPress backend, when a user clicks on the “Login with Google+” button that gets added to the WP log in screen or anywhere via a short code and authenticates their Google Plus account a WordPress account will be created with their G+ information and they will automatically be logged in. Any existing WordPress users can also log in via Google+ and link their two accounts.
If BuddyPress is enabled a Google+ login button will appear on the sidebar login and the registration page. Google+ profile photos will also be imported in as BuddyPress avatars. Members can stream their Google+ activity into their BuddyPress activity if they choose via the Google+ options screen under the logged in BuddyPress members profile settings page. A cron job runs every 30 minutes to import any new Google plus activity from connected users.
Configure Google+ Direct Connect and help visitors find your Google+ page and add it to their circles from directly within a Google Search.
Configure your Google+ Badge and allow visitors to directly connect with and promote your brand on Google+. Visitors can also add your Google+ page to their circles directly from your website. Badges are easy to configure and can be placed on your website via a short code or a widget.

WP Google Plus Connect

Add Google+ Direct Connect Badge & allow your WordPress/BuddyPress users to register or login via their Google+ account & import their stream  …

Nimrod Flores

GooglePlus Multi-Authorship provides a straightforward solution to properly add Google+ Authorship markup to the head of each post and page on a multi-authored site.
It follows the recommended use of the rel=”author” link tag to point to a Google+ profile as described in <a href="http://googlewebmastercentral.blogspot.com/2013/08/relauthor-frequently-asked-advanced.html" rel="nofollow ugc">this FAQ</a> on Google’s official webmaster blog.
<ul>
<li>It adds only the rel=”publisher” link tag on the home page, front page and archive pages</li>
<li>It adds both the rel=”author” and rel=”publisher” on single posts and pages.</li>
<li>The appropriate author’s Google+ profile is used for each single post and page.</li>
<li>You can set a default Google+ profile to be used as a fallback if there’s no Google+ profile specified for an author in his WP user profile settings.</li>
</ul>
For questions and support, please post them at the <a href="http://nimrodflores.com/googleplus-multi-authorship" rel="nofollow ugc">plugin page</a>. I can’t provide quick help if you post your questions in the forum as I am not always in the forums.

GooglePlus Multi-Authorship

GPMA provides a straightforward solution to properly add Google+ Authorship markup to the head of each post and page on a multi-authored site.

WP Google Plus Connect vs GooglePlus Multi-Authorship