Bloafer

Use this plugin to apply <a href="https://wordpress.org/extend/plugins/share-rail/screenshots/" rel="ugc">floating shares</a> to your posts and pages.
This is very similar to the one found on mashable.com.

Share Rail

Use this plugin to apply floating shares to your posts and pages.

Scott Grayban

It puts a bar of icons at the bottom of each post allowing your readers to submit your posts to several different 
social networking and bookmarking sites. (del.icio.us, digg, fark, etc.)
The original plugin was called <a href="http://blog.calevans.com/2006/02/08/notable-another-wordpress-plugin/" rel="nofollow ugc">wp-notable</a> 
but no longer worked or was supported. The author was Cal Evans.

notable

Adds social bookmark links to each blog entry.

Share Rail vs notable