Four Nodes

Simple plugin to display random posts on your wordpress blog. Plugin provides a widget to display random posts in sidebar. 
Also comes with a shortcode [randomposts] to include on pages.
<ul>
<li>Easy to install</li>
<li>Picks Random Posts</li>
<li>Ability to select from specific category</li>
<li>Limit number of posts</li>
<li>Shortcode support</li>
</ul>

FourNodes Random Post

Displays Random wordpress posts in a sidebar widget. Also, provides shortcode to display random posts on pages.

Julian Widya Perdana

It will automatically randomize the displayed post on your homepage and on the feed. It will be useful for site or blog that not daily updated so when the visitor come stopping by on your homepage, he won’t see same posts or contents twice. I hope it will help you keep your blogrank when you don’t have time to manage it.

Post Randomizer

Randomize the posts from your Home and Archive page everytime the visitor load the page

FourNodes Random Post vs Post Randomizer