Sharebar adds a dynamic and fully customizable vertical box to the left of a blog post that can be used for adding social network buttons.
http://wordpress.org/plugins/sharebar/
Widgets · WordPress Plugins
Get access to data on 25,174 websites that are Sharebar for Wordpress Customers. We know of 4,950 live websites using Sharebar for Wordpress and an additional 20,224 sites that used Sharebar for Wordpress historically and 3,095 websites in the United States.
Get a list of 25,174 websites using Sharebar for Wordpress which includes location information, hosting data, contact details, 4,950 currently live websites and an additional 1,278 domains that redirect to sites in this list. 20,224 sites that used this technology previously and 3,095 websites in the United States currently using Sharebar for Wordpress.