PResponsive

This plugin will add a image below your posts, allowing your visitors to share your posts with their friends, on FaceBook, Pinterest, Google+, Twitter, Myspace, Friendfeed, Technorati, del.icio.us, Digg, Google, StumbleUpon, and other. After plugin is activated a buttons will appear after the content of the post.Clicking this button will bring the user to the bookmarking site. If the user isn’t logged in they will be prompted to do so. 
Post your articles to the social bookmarking sites and get traffic.

WP Social Bookmarking

WP Social Bookmarking plugin syndicates your blog posts in social networking sites.

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fabiancz

This plugin adds a set of cool icons and widgets at the end of your post for your readers to share. Widgets are Twitter, Facebook and Google +1. It supports large icons and small icons.
This plugin is copy of “simple-social-sharing-widgets-icons”, because it’s not updated;

Simple Social – Sharing Widgets & Icons Updated

Adds a set of cool icons and widgets at the end of your post for your readers to share.

WP Social Bookmarking vs Simple Social – Sharing Widgets & Icons Updated