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  …

LinksAlpha

Try the plugin at: http://sd.linksalpha.com
Shows links to your Social Networking profiles in a sidebar widget. Supported networks include:
<ol>
<li>Google +1</li>
<li>Facebook Like</li>
<li>Twitter button</li>
<li>LinkedIn </li>
<li>Pinterest</li>
<li>StumbleUpon</li>
<li>YouTube</li>
<li>About.me</li>
<li>Xing</li>
<li>foursquare</li>
<li>RSS</li>
</ol>
List of Features
<ul>
<li>Social Sharing Buttons.</li>
<li>Displays Social Buttons with count of activity.</li>
<li>Offers consistent UI: aligned buttons and uniform color selection.</li>
<li>Enables you to show links to your profile on 11 different Social Networks.</li>
<li>Automatically configure Facebook like and +1 button with your domain. </li>
</ul>
Manual positioning
For Manually positioning the Follow and Subscribe Sidebar Widget in your blog, place the below given code in the sidebar.php below div with id=”secondary” or any other file as you see appropriate in themes folder (…\wordpress\wp-content\themes). 
1. <code><?php lafs_widget_function();?></code>
Benefits
<ul>
<li>Automatic configured Facebook like and +1 button on your site/blog.</li>
<li>Keep your fans, followers, and connections automatically updated on your blog posts.</li>
<li>Expand your blog reach and save time.</li>
</ul>
Misc
<ul>
<li>For getting support, email us at: discuss@linksalpha.com</li>
<li>Note: We encourage you to download the latest version of the plugin as soon as it becomes available – as it may have additional extremely useful features for your blog.</li>
</ul>

Follow and Subscribe

Try the plugin at: http://sd.linksalpha.com

WP Google Plus Connect vs Follow and Subscribe