rockgod100

This plugin creates an area for site admins to jot down post ideas or assign post topics to content authors. Additionally, authors can be given due dates and suggested post types (article, video, etc).
Admins can also e-mail authors directly through the interface using an extension of the wp_mail() function.

Topic Manger

A quick way to remember post topics for single or multi-author blogs

Gianluigi Filippelli

<a href="https://wordpress.org/plugins/co-authors-plus/" rel="ugc">Co-Authors Plus</a> is one of the most useful plugin for multiple authors blogs. This plugin add a widget to add users’ avatars to post also for guest authors and for posts with multiple authors. 
You can also add avatars with a shordcode [blog-post-coauthors]. 
The plugin add also a slider in order to show user’s profile. If you want change the style, you can modify blog-spoiler.css file in the plugin folder.

Co-Authors Widget

The plugin add a widget and a shortcode in order to show authors of an article. It is compatible with Co-Authors Plus.

Topic Manger vs Co-Authors Widget