elojografico

This plugins allows us to insert share buttons in the single post view, with no loading pain.
At this moment, it works with Facebook, Google+, Twitter and Whatsapp (this last only when displaying on mobile devices).
It has just a few options to configure it, and works fine with no special requirements.
If you like it, please rate it and any review, comment, question or petition will be welcomed.

EOG Simplest Share Buttons

Adds buttons to blog posts that allow the visitor to share the content in his favourite social network.

straps

Dynamic widget to insert classic social buttons and counters on your sidebar. 
Title changes based on page type users are visiting (Home, pages and posts). 
Insert a comma separated list of social sites in the order you want and start sharing. 
Play with all of the configuration options to reach the best visual appeal. 
Never forget to share your posts anymore and start increase visitors for your web site. 
Internationalization support via widget admin added.
See also: <a href="http://www.strx.it/2010/11/simple-sharing-wordpress-widget/" rel="nofollow ugc">Official Blog Post</a>.

Strx Simple Sharing Sidebar Widget

Dynamic widget to insert classic social buttons and counters on your sidebar.

EOG Simplest Share Buttons vs Strx Simple Sharing Sidebar Widget