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.

Thamizhchelvan

Will add bookmark icon for each post and page to share with popular social bookmarking sites.

Simple Social Bookmarking Plugin

Will add bookmark icon for each post and page to share with popular social bookmarking sites.

Share Rail vs Simple Social Bookmarking Plugin