Brian Onorio, O3

This plugin makes syndicating your content to social networks easy. While other plugins have 100s of available networks you can connect to, this plugin makes it easy to post share buttons for the 4 big networks: Facebook, Twitter, Google+, and LinkedIn. Who uses Ying Yang and Bamalamadingdong anyway? Once activated, you will see a series of social plugins at the bottom of each post allowing your site visitors to quickly and easily post the content on your site to their profiles on these networks.
The plugin has a robust options panel allowing you to pick and choose which networks to support. You can also customize the Facebook and Twitter plugins in the exact same was as you would be able to if you were pulling the plugin code directly from the supporting website.
Default Options include:
<ul>
<li>Choice of any or all of the following networks: Twitter, Facebook, Google+, and LinkedIn</li>
<li>Customization of tweet content allowing you to use to use the page title or to customize it</li>
<li>Add a Twitter user to the tweets</li>
<li>Add a hashtag to tweets</li>
<li>Include or exclude the Facebook Send button</li>
<li>Choice between Facebook verb to use (Like or Recommend)</li>
<li>Option to include default styles or leaving the styling up to you</li>
<li>Place the Social Plugins above the Post Content, below the Post Content, above and below the Post Content, or place them manually</li>
<li>Restrict the Social Plugins to just the posts, pages, or any other registered custom post type</li>
</ul>
For more information on this plugin and support for this plugin, visit <a href="http://www.weareo3.com/plugins/o3-social-share/" rel="nofollow ugc">O3 Social Share on O3</a>.
Note: The Facebook “Send” button, when activated, sometimes disappears on some browsers after a momentary display. This seems to be connected to a Facebook bug documented here: <a href="https://developers.facebook.com/bugs/299191993489218?browse=search_4f9eab716e1110276007093" rel="nofollow ugc">Facebook</a>.
<h3>Usage</h3>
Simply activate the plugin and you’re all set.

O3 Social Share

This plugin will add social share icons for the 4 major networks to the bottom of WordPress posts.

H. Peter Pfeufer

Add a sidebarwidget to display the count of your twitterfollowers, your googleplus circles, fans of your facebook-fanpage, and your feedreaders (from feedburner) in your sidebar.
Features
<ul>
<li>Easy install</li>
<li>Panel for easy configuration</li>
<li>No external scripts</li>
<li>Cleaning up database on uninstall</li>
</ul>
Languages
<ul>
<li>German</li>
<li>English</li>
</ul>

O3 Social Share vs Social Impact Widget