phpgeekfr

This plugin replaces author links of your posts with your Google+ Profile Link. 
This allow your Google+ Profile picture to be displayed in Google search results. 
It Works for single author and multi-author WordPress sites.

Basic Google Authorship

This plugin replaces author links of your posts with your Google+ Profile Link.

mlazarov

Google Plus Profile Picture appear in Google Search. Integrate Google Plus Profile with WordPress. Make your website come up in Google.
Including Google authorship for multiple authors and for wordpress multisite
Just 3 easy steps to process: 
1. Plugin Installation 
2. Enter Google Profile URL in Profile Page 
3. Post a link back from Google Plus Profile to Your Current Website

Google Plus Authorship

Add Google Plus Profile Picture to Google Search Results. Very Easy to implement! Google authorship for multiple authors

Basic Google Authorship vs Google Plus Authorship