Anti-Spam SMTP Proxy Server implements multiple spam filters
Anti Spam SMTP Gateway
CIDRAM: Classless Inter-Domain Routing Access Manager.
Google Apps Script to send third party recruiter email to spam
Open-Source Phishing Framework
Remote anti spam utility
An easy-to-use anti-spam email gateway
Block or allow connections by country address blocks
Open Source Anti-Spam and Anti-Virus Gateway
Virtual Appliance of RadicalSpam
Realtime Anti-Phishing Training Online Resource
A simple PHP-AJAX captcha application
This Plugin provides very simple and powerful captcha for your blog
Advertising domain filtering list
Catch-a spammer with a CAPTCHA.