This plugin allows you to easily insert a wide variety of links into your wordpress documents with the following tag style:
[ln wikipedia]topic[/ln]
[ln php]htmlentities[/ln]
[ln amazon]978-0321396853[text]Eclipse Web Tools Platform[/text][/ln]
Or you can add links by clicking the ‘ln’ button inside of the wysiwyg editor. This will bring up a dialog box where you enter in the necessary data for that particular link
New link types can be easily added and existing links can be easily modified from the wordpress options page.
The following types of links are currently supported by default (with more on the way):
<ul>
<li>amazon</li>
<li>gravatar</li>
<li>php</li>
<li>twitter-rss</li>
<li>wikipedia</li>
<li>wppost</li>
</ul>

linkle

Easily embed links to wikipedia topics, amazon book sales, php documentation, and more with [ln linktype]topic[/ln].

Mikael Korpela

See today’s Wikimedia Commons picture of the day behind WordPress login screen.
https://commons.wikimedia.org/wiki/Commons:Picture_of_the_day
If you ended up here by searching, you might also be interested in 
pure PHP class which gives you URL of the PotD:
https://github.com/simison/WikimediaCommonsPotd

Wikimedia Commons Picture of The Day for WP Login

See today's Wikimedia Commons picture of the day behind WordPress login screen.

linkle vs Wikimedia Commons Picture of The Day for WP Login