hostinginfo360

This plugin will collect Google Page Rank and Alexa Rank and display it in the footer of your blog. 
The result will be collected 1 time each day.
This release is compatible with all WordPress versions since 3.0.
<h3>License</h3>
Good news, this plugin is free for everyone! Since it’s released under the GPL, you can use it free of charge on your personal or commercial blog.

Web Rank Get

This plugin will collect Google Page Rank and Alexa Rank and display it in the footer of your blog.

fliptel

Displays the Alexa traffic rank in the sidebar of your blog via widget interface or anywhere else via function call. The Plugin comes with 5 different layouts.
Browse more <a href="http://www.fliptel.de/wordpress-plugins" title="Wordpress Plugins" rel="nofollow ugc">WordPress Plugins</a> by <a href="http://www.fliptel.de" title="Fliptel" rel="nofollow ugc">Fliptel</a>.

AlexaRank

Displays the Alexa traffic rank in the sidebar of your blog via widget interface or anywhere else via function call.

Web Rank Get vs AlexaRank