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  …

lucha

A simple interface to a jQuery plug-in, originally written by heisde.de and thereafter re-written by the author.
The plugins offers the possibility of showing in posts (and optionally pages) buttons for sharing content to Facebook, Google Plus, Twitter, and Identi.ca. These buttons are dummy-button by default, and only after explicit action by the visitor they are activated and become the real buttons. This allows to give control to the single visitor if he wants to send 
sensible personal information to third-parties sites, and thus providing a nice compromise between privacy and social sharing.

Privacy Share Buttons

Enables the well-known "Share this" buttons for different social networks, but with respect toward's your user privacy and data.

WP Google Plus Connect vs Privacy Share Buttons