• Anti-Spam ACP by EXreaction

• vbStopForumSpam by pedigree (vB 3.6-3.8, 4.0) no longer in development
• Spam-O-Matic by GlowHost.com (vB 4.0+)

• Stop Spammer by Snoopy

• Stopforumspam.com for MyBB

• Stopforumspam.com Antispam for PunBB by grez, keydog and slavok

• Antispam mod for bots by Tyger

• Stop Forum Spam by King Kovifor
• XenUtiles by Jaxel

• Spam Login Filter by Ray J
• Anti Spam'mer plugin for Elgg by Team Webgalli

• Stop Forum Spam by designermonkey

• Stop Forum Spam Integration v0.3 by Gizmo

• SFS Global Antispam by chuckroast

• MX Stop Spammers by Max @ eec

• Module: StopForumSpam by Thomas Seifert

• Forum Spammer IP & Email Check via stopforumspam by Shady
• Add Stop Forum Spam IP Check to Admin New Registration Notification Email by Mod-Mall.com

• StopForumSpam by Fabo

• StopForumSpam Mod for YaBB 2.5 (mirror) by Derek Barnstorm

Blog Mods

• Stop Spammer Registrations by Keith Graham

Framework Systems

• stopforumspam 1.0.1 middleware

Other Stuff

FSLC by gunner. The best GUI tool for searching this (and other) sites

Rail/3 plugin for model validation by rfc2822 and the GEM wrapper by Lake Denman.

StopForumSpam Integration Library for PHP 5.2.3+ by Obsidian

API wrapper in Ruby by Lake Denman (more info)

Spambot Search Tool by MysteryCFM. Queries 8 sources of spam lists, including this site. See how to integrate the script with a variety of software.

Lothy has written a Firefox search plugin using the Mycroft Project.

Smurf_Minions wrote a spambot detector in PHP using the API. The source is included as well.

kacarstensen has written a Python library for interfacing with the site.