onlineth

A pluginized version of ReadRemaining.js
Tell your readers how long they’ll need to get through all of your gibberish, with this clever jQuery plugin. With WP ReadRemaining TL;DR is a thing of the past.
Personalized – The time is estimated based on the user scrolling speed Non-Annoying – It is set to appear only when the user is actually reading. 
Fully customizable – Bold Comic Sans? No problem, just set the css. But… why? 
Flexible layout – Takes into account text, images or even videos.

WP ReadRemaining

This WordPress plugin allows you to show the user how long it will take to read the article considering the speed in which the user is scrolling.

TomHarrigan

jmarx75

codeandtheory

In addition to normal infinite scroll behavior, this plugin adds infinite scroll to the single post page. When reading a single post, once the reader reaches the bottom of the page, the next post loads in. This is similar to functionality on big news sites such as Time.com, LA Times, Quartz, Vogue.com
The default WordPress TwentySomething themes, Genesis themes and Canvas themes are already compatable with this plugin and ready to go!
Relies on add_theme_support. If your theme is not in the above list, add the folliwing to your themes functions.php file: <code>add_theme_support( 'infinite-transporter' );</code>
See installation and FAQ sections for more on getting set up.

Infinite Post Transporter

Infinite scroll extended to single post pages

WP ReadRemaining vs Infinite Post Transporter