WP-reCAPTCHA
admin, on March 27th, 2009 
Wp-reCAPTCHA is an anti-spam method originating from Carnegie Mellon University. It prevents misuse of the comments feature. The only requirements for this plugin are that you get the API keys for reCAPTCHA. This is easy enough to do within a minute or so.
You can activate this plugin in your control panel. For information on how to use this plugin, please visit:
http://www.blaenkdenum.com/wp-recaptcha/
http://recaptcha.net/whyrecaptcha.html (get the API keys here; simply follow the instructions)
Plugin Info: Version 2.8.5
