wondermill

If you want to graphically display a random list of your posts with their featured image in the side bar, then this is the plugin for you. This plugin allows you to set the category IDs (or all categories) you want to pull the random posts from, the number of random posts to display, the maximum width and height of the featured image thumbnail, the widget title, and the colors of the surrounding box.

Random Posts with Thumbnails

Puts a list of clickable random posts with their featured image in your sidebar as a widget, this list is customizable.

dyersorg

<a href="http://www.dyers.org/blog/better-blogroll-widget-for-wordpress/#changelog" title="Better Blogroll Change log" rel="nofollow ugc">Changelog</a>
The Better Blogroll widget for WordPress allows you to display a configurable number of random links from your WordPress blogroll. This should help to combat link blindness while still letting you to share the link love with more of your favorite blogs.
Some Features:
<ul>
<li>Links can be sorted randomly, by title, or by rating.</li>
<li>The number of links shown is configurable.</li>
<li>Categories from which links are shown is configurable.</li>
<li>Links can be set to “nofollow” if your links are coming from paid sources.</li>
<li>Capable of Displaying XFN Data.</li>
<li>Displays image links, text links, or both.</li>
<li>Links can be in a single list or separated by category.</li>
<li>Can display each link’s category or rating to its right.</li>
<li>The description of each link appears in a tool tip.</li>
<li>Allows you to show an explanation that the list is a rolling blogroll.</li>
</ul>

Better Blogroll

Allows you to display a configurable number of random links from your Wordpress blogroll

Random Posts with Thumbnails vs Better Blogroll