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.

pantsonhead

RandomText is a handy WordPress plugin that allows you to save, edit and delete categorized text, and inject random/rotated text by category into the sidebar (via widget) or page body (via template tags). The sidebar widget allows you to set an optional Title, and text header and footer. You could say RandomText picks up where the Text widget left off. Whether you want to display random/rotated trivia, quotes, helpful hints, featured articles, or snippets of html, you can do it all easily with RandomText.

Random Text

Store and display random/rotated text by category in sidebar widget or templates.

Random Posts Within Date Range Widget vs Random Text