Jo Sprague

Quotable adds buttons to quotes and text selection that make it quick and easy for your readers to share quotes from your website.
Simply install the plugin, there is no setup required. Icons that match your site’s theme will be added to quotes and appear in a contextual menu when readers select text on your website, allowing them to quickly and easily share the quotes to Twitter.
This plugin adds a page link, hashtags and mentions to shared quotes. WordPress tags are used as hashtags and, if you use Yoast’s WordPress SEO plugin, the post author’s and site’s Twitter accounts are added as mentions to Tweets.
<h3>Sponsorship</h3>
I am software engineer and I love to create free and open source software for nomads, bloggers and language learners. In order to afford to spend time creating, maintaining and updating my free software, I rely on financial support from donors. In return, I provide my donors with access to exclusive updates, support and features. If you find this plugin useful, please consider <a href="https://www.patreon.com/localjo" rel="nofollow ugc">supporting me for just $1/month on Patreon</a>.

Quotable

Adds buttons to quotes and text selection that make it quick and easy for your readers to share quotes from your website.

inboundrocket

jcvangent

Selection Sharer makes it super easy for your readers to share your content and drive new visitors to your site. With Selection Sharer, any visitor on your website/blog can easily 
highlight any part of your content and share it immediately on Twitter, Facebook, LinkedIn or via email. Ultimately, the more your readers share, the more new traffic your site will get.
When a visitor highlights some text on your WordPress website they will be presented by a Medium like popover menu to share their highlighted content. This plugin supports both desktop (with a pop-over) as well as mobile devices (with a pop-under). This plugin is made possible by the excellent work done by <a href="https://github.com/xdamman/selection-sharer" rel="nofollow ugc">@xdamman</a> and is based on his code.

Selection Sharer by Hans van Gent

Works great!

Medium like popover menu to share on Twitter, Facebook, LinkedIn or by email any text selected on the page.

Quotable vs Selection Sharer by Hans van Gent