wppal

Easy Captcha is an ideal solution for those who want to try different types of captcha to achieve an optimal site usability and captcha protection ratio. It allows a WordPress site owner to choose which captcha should be used on a particular page.
Currently the plugin supports 3 types of captcha:
<ul>
<li>Hidden captcha, </li>
<li>Simple image captcha,</li>
<li>Google reCaptcha</li>
</ul>
Hidden Captcha is invisible to site visitors and does not assume any specific user actions. It just checks that a visitor behaves like a human. Although it might seem that Hidden Captcha does not fully correspond to the definition of CAPTCHA (found at the end of the FAQ), it still distinguishes a human from a bot based on natural human behavior. Hidden Captcha also allows checking whether a visitor’s browser has JavaScript and Cookies enabled.
Simple Captcha works in a traditional manner: it shows an image and requires a user to enter a captcha code. Simple Captcha stores captcha values on the server side using a custom session approach.
reCaptcha is a reliable and powerful captcha service provided by Google for free. Please visit <a href="http://google.com/recaptcha" rel="nofollow ugc">reCaptcha site</a> for more details
Any type of captcha from above may be added to the following WordPress site places:
<ul>
<li>Comment forms,</li>
<li>Login page,</li>
<li>Registration page,</li>
<li>Password reset page. </li>
</ul>
With Easy Captcha you can easily install different types of captcha on each individual page.
Please read the FAQ and Installation sections for more details.

Easy Captcha

Several types of captcha to protect your site in one easy to use plugin.

Geek Goddess

NOTICE: This plugin will no longer be supported nor updated. Infusionsoft has now added Google’s reCaptcha into their forms natively, so this plugin is no longer needed.
Infusionsoft® has a native captcha you can insert into web forms, but it’s not user-friendly, blocks submissions, and is ugly. With the new reCAPTCHA API, Google has released a captcha that the bulk of your users will only have to check a box to pass, optimizing opt-ins while protecting you from inserting spam into your Infusionsoft automation.
As a bonus, activating this plugin in an Infusionsoft web form will also set up basic HTML5 form validation for it.
Requires PHP 5.2+ for json support

GG Infucaptcha reCaptcha for Infusionsoft

Inserts Google’s new reCAPTCHA into Infusionsoft web forms

Easy Captcha vs GG Infucaptcha reCaptcha for Infusionsoft