Captcha Bank is an easy to use wordpress security plugin to prevent spam on your site while letting real people pass through with ease.
This antispam plugin provides very simple(one-click) and powerful captcha for your blog.
PlusCaptcha - The Easiest Captcha to Setup and Execute, with an Auto-Setup Feature! Trusted by thousands of blog, e-commerce, and government sites!
Stop spam bots from registering, logging in, filling out contact forms and commenting on your site without using annoying Captcha codes or puzzles.
The Add new recaptcha google plugin allows you to implement a super security REcaptcha form into web forms.