Very simple, yet effective and flexible plugin. There are a number of styles to choose from and options like opening the share in a new window.
It can be added to the top of the posts, bottom, or both. It also be applied to just pages, posts, or media. You can also just use the shortcodes on 'want' basis.
Perhaps a sidebar plugin version of this could be a good addition to the repository.
Thumbs up to Geoffrey, the creator.