FormSpamCheck is a PHP class to centrally manage several online form and forum spam services. It currently supports www.stopforumspam.com, www.projecthoneypot.org, and www.akismet.com.
Defender is a wrapper for the Defensio spam filtering API. More than just another spam filter, Defensio also eliminates malware and other unwanted or risky content to protect your blog or Web 2.0 application.
A game of competitive puzzle design.
A foundation class library.