Puts a list of clickable random posts with their featured image in your sidebar as a widget, this list is customizable.
How do I install and use:
Activate the Plugin 'Random Posts with Thumbnails' in the Plugins List.
Click 'Appearance' in the WordPress admin menu and then click 'Widgets' in the sub-menu of 'Appearance'.
Drag 'Random Posts with Thumbnails' from Available Widgets to the Widget area you want it to display it in (the Primary Widget Area is my side bar and where I put this Widget).
The widget has pre-settings to start with but you can change them to your liking.
(side note: This plugin uses the Featured Image of a Post to display a thumbnail image in the Random Posts list, if your Posts do not have a Featured Image set then there will be no thumbnail image on that post in the list.)