Simple Captcha : Zero Dependecy Captcha for Rails

Finally after long wait, the next stable release of the fun-du, simple
and useful plugin SimpleCaptcha is here!.

Major changes have been incorporated to the plugin in this release
1.2.0

Which includes...

    * No Pre-Requisites
    * RMagick NOT required anymore
    * FileSystem Usage Removed
    * No third part dependency(NO API call!)
    * Works Perfectly with Multiple Clustered Servers
    * A completely local application based ZERO DEPENDENCY CAPTCHA

And many more...
Read here( http://expressica.com/simple_captcha ) for implementation,
usage and examples.