Jonathan Fleury

This is a “draggable” captcha. Images have to be dragged into ascending order.
IMPORTANT : This pluggin require PHP 5.4 and GD extension.

Guroot Captcha

This is a "draggable" captcha. Images have to be dragged into ascending order.

Daniel Davis

No-captcha Spam Block is a WordPress plugin that automatically blocks comments it thinks are spam. It works tirelessly, day and night, applying various checks to each comment that comes in and giving it a spam score – any score too high and the comment goes straight to the spam bucket in disgrace.
<ul>
<li>No third-party registration</li>
<li>No JavaScript required</li>
<li>Best of all, no captchas</li>
</ul>
There are no visible changes to your website and you don’t need to set anything up – just install, activate and go!

No-captcha Spam Block

Dramatically reduce comment spam on your blog without using a captcha.

Guroot Captcha vs No-captcha Spam Block