This plugin creates a resistor color code captcha on comment forms
AdCaptcher.com enables you to build custom captchas. You need an AdCaptcher account to administrate your custom captchas.
A widget for the WP-invites plugin
Provides functions to easily display and validate a reCAPTCHA
WP Simple Contact Form is a basic contact form with css styling, form validation, error feedback and captcha spam check.
Anonymous Posting plugin allows anonymous user to write their own posts using special page, no access to WP panel is needed.
With this plugin, you can manage a simple support ticket system on your WordPress.
Based on Takayuki Miyoshi’s Contact Form 7 version 2.0.1. Has better support for checkboxes (clickable labels, actually separate onto different line
The plugin provides the next generation in captcha, BotProof Captcha 2.0, to a WordPress blog comment form. It is currently version 0.9.6.8 Beta.
Integrates a logic captcha to verify that the registrant is a human and not a spam bot instead of using distorted images or audio.
ImHuman provides more humane, fun, easy, secure and mostly user friendly captcha (are you really a human?) detection for posting comments.
Create customizable contact forms and sticky contact button for your WordPress blog. Web 2.0 style.
figlet math challenge, captcha replacement, based on TryMath php class and phpFiglet
Photo Captcha with user defined images to reduce the spambot prize/payload to one website at a time. A captcha with "Which one of these things is not
Pictcha is a very unique & secure CAPTCHA.
Adds a CAPTCHA to account registration that uses Vidoop's ImageShield.
A script which protects the comment form from spam. Does four ways of protection.
Let admin create a page to do automatic exchange links with other webmaster
Security Captcha es un sistema para prevenir spam de cualquier tito, tanto por personas como por scripts creados por personas.
Allows you to display a captcha on your comment form to avoid spam.
Add a captcha to protect comments from being spammed using Cryptographp library.