This plugin utilizes reCAPTCHA to help your blog stay clear of spam-registrations.
Add reCAPTCHA to your WordPress login form
Modification of the original Tiny Contact Form by Tom Braider to use Google's recaptcha service.
Enables display of an AJAX driven contact form when a user clicks on links with a specified class.
Captcha Animal protects your user registration and comments with a test of identifying two friendly animals.
Anonymous Posting plugin allows anonymous user to write their own posts using special page, no access to WP panel is needed.
Recapture fights user registration spam by placing a reCAPTCHA on the user registration form.
Automatically scans for emails and hides them from spammers using the reCAPTCHA Mailhide API. Nothing in the database is
actually modified, it's just
RSS link for this tag.