• 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 - Only use versions 1.1.6 and above

• 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 for WoltLab Burning Board by SoftCreatR

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

• Spambot

• nodejs wrapper for the StopForumSpam.com REST by Ted Winslow (deltreey)

Blog Mods

• Stop Spammer Registrations by Keith Graham
• AVH First Defense Against Spam by Peter Vanderdoes

Framework Systems

• stopforumspam 1.0.1 middleware

Java

• Client Library for java by kohsuke Github source

Github

SpamProtection A PHP spam protection class for use in contact forms and comment fields, with TOR node configuration support by Helge Sverre

phpBB-SFS-hook A hook to query if an IP is located in the database of stopforumspam.com by k0nsl

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

Ban Comment Spam by "ToodlePip" - A Python script to ban IPs found in your logs, at the firewall.

Other Stuff

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

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.