Unity Captcha is a gem that use two levels of Captcha. First level is about Left Hemisphere: Logic and Math. Second level is about Right Hemisphere: Intuition and Drawing. This two levels functioning in complete harmony creates unity and this is the base design of this Captcha.

Captcha Client for YunPian.com

Anti-spam protection for your website

Merb plugin that provides resource access rate limits and captcha'ing

A gem to generate captcha pictures.

Ruby port of VIT AutoCaptcha

Description of RailsCaptcha.

This plugin adds helpers for the YinXiangMa CAPTCHA API

Forked from https://github.com/kares/simple_captcha

A simple and custom captcha for Rails3.

This is mt first gem

This is a Captcha gem for Rails Applications. It drawing captcha image with C code so it no dependencies.

A simple image captcha gem

Captcha form Jike API

RedisCaptcha provides simple captcha that can be read by human.

Merb plugin that provides resource access rate limits and captcha'ing

Submit captcha images and retrieve the text as a string.

Display and verify arcaptcha service captcha

you will get arithmatic sum with answer you just have to compare with ur user in controller

Metabypass | Ruby-based easy implementation for solving any type of captcha by Metabypass