Hung Trang Si

This plugin add “Simple Random Posts” widget on Widget Panel, help display random posts in your blogroll. This widget has 4 layouts for you choose

SB Random Posts Widget

Simple way display random posts in your blogroll

Fubra

ray.viljoen

The plugin provides a sidebar widget with customisable title and number of related posts to display. 
The widget will display a random list of x number of posts ( selected in widget options ) together with a small tag including the publish date and author. 
If used outside of a specific category the widget will default to all categories, whilst still displaying the selected number of random posts.
Developed by <a href="http://www.catn.com" rel="nofollow ugc">PHP Hosting Experts CatN</a>

Random Related Posts

A simple sidebar widget to include a custom number of posts from the same category as the current post.

SB Random Posts Widget vs Random Related Posts