How to: Captchas and anti-spam
* [ActsAsTextcaptcha](https://github.com/matthutchinson/acts_as_textcaptcha) - Protection for Rails models with text-based logic question captchas (from Rob Tuley's textcaptcha.com)
* [Invisible Captcha](https://github.com/markets/invisible_captcha) - Unobtrusive and flexible spam protection based on the honeypot strategy. It also provides a time-sensitive form submission.
* [Rakismet](https://github.com/joshfrench/rakismet) - Easy Akismet and TypePad AntiSpam integration for Rails.
* [reCAPTCHA](https://github.com/ambethia/recaptcha) - reCaptcha API helpers for ruby apps.
* [Voight-Kampff](https://github.com/biola/Voight-Kampff) - A Ruby gem that detects bots, spiders, crawlers and replicants.