Singlefin
iPrism - Monitor and Report on Internet use. iPrism is the #1 Web filtering appliance. iPrism utilizes iGuard the top url filtering database for internet content filtering.
http://www.singlefin.net

CyberGuard
ICSA and NSA certified Unixware and NT-based filtering firewall. Offers static packet filtering, dynamic packet filtering (stateful inspection) and proxy gateway (smart proxies).
http://www.cyberguard.com/

GSEC1
Prodigy devices offer SPI, antivirus,intrusion detection, VPN bandwidth management and content filtering for web and email access.
http://www.gsec1.com/

SnapGear
Secure SnapGear is one of the most feature rich, cost effective, and flexible firewall security appliances available. Intended for the SMB/SME, the telecommuter, or even the large distributed enterprise with centralized management needs, SnapGear includes wide area networking tools normally only available in enterprise-class devices. Not just a single-purpose security appliance, SnapGear includes an anti-virus engine, intrusion detection, and an enterprise-class security event management system. It’s also the first and only small- to medium-sized business appliance to include a proactive reputation-based security system, TrustedSource, to control what is allowed to pass through to your network. Free of per-user and VPN tunnel licensing fees, SnapGear is a scalable VPN device that supports all major protocols, enabling you to manage all remote access requirements into one high-speed, highly reliable, small form-factor appliance.
http://www.snapgear.com

California Micro Devices
Designs and manufactures integrated thin-film, silicon-based termination, filtering and ESD components with active electronic circuitry.
http://www.calmicro.com/

Visual Dorp Filter
DORP - Home of Object Oriented Filtering for Visual FoxPro and SQL developers.DORP-VDF objects are set of date-centric filtering objects and provided to help speed the process of filtering application development.VCX library for VFP8,VFP9 development views and reports.Advice, tips, sample code, downloads.
http://www.dorp-vdf.com

Safer Path Internet
Dialup access with web filtering or add filtering to your existing connection.
http://www.saferpath.com/

SpamEater Pro
Email filtering system that can automatically receive periodic updates to its filtering rules.
http://www.hms.com/spameater.asp

NetMail
Email client. Full-featured e-mail client designed for e-business
http://www.softwarea.com/netmail.htm

HWG Filtering FAQ (Windows, Mac, Unix)
The HTML Writers' Guild's FAQ sheet about mail filtering systems (multiple platforms)
http://www.hwg.org/resources/faqs/filterFAQ.html