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.

lupka

This plugin allows you to create a widget that will display the title/date/excerpt from random posts in a specified(or open-ended) date range. It can also be used outside of a widget to create custom loops of random posts within a date range. The following can be specified:
<ul>
<li>Number of posts to display</li>
<li>Whether or not to show dates</li>
<li>Whether or not to show excerpts</li>
<li>Excerpt length (number of words)</li>
<li>Start date and End date of posts to randomize</li>
<li>Whether or not to always use current date as end. (Allows you to include new posts without editing settings every day)</li>
<li>Option to use relative time instead (To chose from random posts from last week, year, etc.)</li>
<li>Category to choose posts from. (Example: Random posts from sports category in the past week. This is the original reason I needed a plugin like this. Comes in handy for the newspaper site I run.)</li>
</ul>
Please contact me if you run into any issues, either via email (lupka31@gmail.com) or Twitter (http://twitter.com/lupka) 
For latest FAQs/info visit: http://alexchalupka.com/projects/wordpress/random-posts-widget/

Random Posts Within Date Range Widget

Widget that displays the title(w/ link), date(optional), and excerpt(optional) of random posts within a selected date range.

FourNodes Random Post vs Random Posts Within Date Range Widget