An exceptionally powerful WordPress anti-spam plugin that eliminates comment spam, trackback spam, contact form spam & registration spam.
Anti-Captcha is a transparent spam solution that does not require any end-user interaction.
SiteBrains blocks spam posts using a completely configurable set of rules. Both interactively as the user types and on our servers upon submission.
Prevent people from registering with emails that contain a subdomain to help reduce spam.