acts_as_textcaptcha (rubygems):   ActsAsTextcaptcha provides spam protection for Rails models with text-based   logic question captchas. Questions are fetched from Rob Tuley's   textcaptcha.com They can be solved easily by humans but are tough for robots   to crack. 
Keywords: activerecord|captcha|captcha-alternative|captcha-generator|rails|ruby|spam-protection