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.
Add Google’s simple checkbox reCAPTCHA to WordPress wp-admin login page.
The Add new recaptcha google plugin allows you to implement a super security REcaptcha form into web forms.