FasterThemes

Quick Whois WordPress Plugin Shows whois information of the provided domain name. You can use Widget in the sidebar or you can also use Shortcode in the pages/posts.
<a href="http://whois.fasterthemes.com/" rel="nofollow ugc">DEMO of Quick Whois plugin</a>
Features:
<ul>
<li>You can use this plugin in your sidebar by dragging and dropping “Quick Whois” Widget.</li>
<li>You can use this in any specific page/post by putting shortcode [quick_whois].</li>
<li>This plugin converts your website into a whois data provider website in a few seconds !</li>
</ul>
<h3>License and Copyrights for Resources used in this plugin</h3>
i) We have used phpwhois.org php script from this website http://www.phpwhois.org Copyright which is a free software and we are allowed to redistribute it and/or 
modify it under the terms of the GNU General Public License v2.
<pre><code>For any help you can mail us at support[at]fasterthemes.com
</code></pre>

Quick Whois

Quick Whois Plugin Shows Whois information of the provided domain name.  You can do this using Widget/Shortcode.

cavimaster

Simple whois tool in a widget
Post a domain name et submit. 
Whois on widget return to you a complet whois query into Jquery lightbox. 
You can use shortcode like: [WHOIS] for put it in your page or post.
<a href="http://www.devsector.ch/cavimaster/category/developpement/wordpress-plugins-widgets" rel="nofollow ugc">Cavimaster_blog</a>
Original PHP whois code by Sven Cailteux – <a href="http://www.dimension-internet.com" rel="nofollow ugc">Dimension internet</a>

Quick Whois vs Whois on widget