skipstorm

This plugin displays in a widget the latest image from XKCD. It requires php 5.0 to work with curl and dom enabled, features included in most hosting. XKCD images are under creative commons licence so you’re free to display them on your site but you can’t remove the link.
I’m in no way related to XKCD, dough i admire that guy, so i’m not responsible for the content of the website. 
I did not ask permission to create this widget but as mentioned creative commons and so on.

Sk XKCD Widget

This plugin displays in a widget the latest image from XKCD.

Dan Griffiths

Allows display of XKCD comics through a simple widget or shortcode. Both can be configured to display the latest comic, a random comic, or a specific comic.
For example, to display comic 100 using the shortcode, simply put the shortcode [xkcd id=”100″] where you want it to be shown.
[xkcd id=”random” title=”false”] will display a random comic, without the title.

XKCD Embed

A simple plugin to display XKCD comics on your website.

Sk XKCD Widget vs XKCD Embed