Dana Ross

Read Later Buttons provides a widget and a shortcode for displaying “read later” buttons for the popular apps Instapaper, Pocket, and Readability. It can also display a <a href="https://wordpress.org/extend/plugins/send-to-kindle/" rel="ugc">Send to Kindle</a> button if that plugin is installed, letting your users send your content to their e-reader to enoy when they have the time.
This plugin is designed to function well and look good without much fuss, but it also provides a shortcode and filters so you can control how the buttons look & work.
Shortcode
Use the <code>[read_later_buttons]</code> shortcode to render buttons for every one of the supported services. You can also include the names of one or more services (i.e. <code>[read_later_buttons instapaper pocket]</code>) to just get those buttons. Valid service names are <code>kindle</code>, <code>instapaper</code>, <code>pocket</code>, and <code>readlater</code>.
The shortcode can also display an estimated reading time if you include the “time” parameter (<code>[read_later_buttons time]</code>). The reading time can be combined with service names (<code>[read_later_buttons time instapaper]</code>) and the time will render above the buttons. When including the time estimate, the plugin won’t display all the buttons by default. You need to include the “all” parameter (i.e. <code>[read_later_buttons time all]</code>) in that case. Also, the shortcode has to be used inside “the loop” in order to calculate a time — in other words in a page, post, or the appropriate parts of your theme template.
Filters
<ol>
<li>read_later_buttons_do_css: return false to prevent loading the default CSS (doesn’t affect the Kindle plugin)</li>
<li>read_later_buttons_instapaper: alter the HTML generated for the Instapaper button</li>
<li>read_later_buttons_pocket: alter the HTML generated for the Pocket button</li>
<li>read_later_buttons_readability: alter the HTML generated for the Readability button</li>
<li>read_later_buttons_reading_time: alter the HTML generated for the reading time estimate</li>
<li>read_later_buttons_link: alter or replace the link passed to the read later services (doesn’t affect the Kindle plugin)</li>
</ol>

Read Later Buttons

Adds "read later" buttons to a site. Can send content to Kindle (additional plugin required), Instapaper, Pocket, and Readability.

Pierre-Andre Dewitte

Make your users save time to read later your thrilling content by adding the official buttons from the most used apps around the world : Pocket, Instapaper, Readability and since v1.1 Kindle ! 
Choose which one you want to display, which size, when and where to display them (posts, articles, both, at the start/end/both of content).
Look at the changelog tab to see new features !
More features in progress…
<h3>Why this plugin</h3>
Apps like Pocket, Readability & Instapaper are used by tens of millions around the world, especially to save long and captivating articles to read it later offline. 
Usually, to save an article from a mobile device, you have to click three times. (The Menu button, then Share button, then Add to Pocket, or any app you use). 
In the long run, it’s painful for users. And if it’s painful for users, it’s not good for your blog.

Pocket Readability Instapaper Buttons

Display official Pocket Instapaper and Readability buttons to your posts/pages.

Read Later Buttons vs Pocket Readability Instapaper Buttons