Free Personal Firewalls
Guarddog
Guarddog is a firewall configuration utility for Linux systems. Guarddog is aimed at two groups of users. Novice to intermediate users who are not experts in TCP/IP networking and security, and those users who don't want the hastle of dealing with cryptic shell scripts and ipchains/iptables parameters.
SoftPerfect Personal Firewall
SoftPerfect Personal Firewall is a free network firewall designed to protect your PC against attacks from the Internet or via a local area network. SoftPerfect Personal Firewall offers customizable security using user-defined rules for packet filtering. It works at a low level and also allows you to create rules based on non-IP protocols such as ARP.
SmoothWall Express
SmoothWall Express is an open source firewall distribution based on the GNU/Linux operating system. SmoothWall Express is intended for use by anyone from a home user to a systems administrator. It can run on almost any PC from a 486 upwards, which becomes a dedicated firewall appliance (the SmoothWall box).
Firestarter
Firestarter is an Open Source visual firewall program. The software aims to combine ease of use with powerful features, therefore serving both Linux desktop users and system administrators.
ZoneAlarm
Excellent free firewall for windows that is free for personal use.
Kerio
Kerio Personal Firewall is FREE for home and personal use.
Jetico Personal Firewall for Windows 98/ME/NT/2000/XP
Jetico Personal Firewall performs Stateful Inspection of applications' network activity. It means that the firewall examines the states of all internet connections, looking for the telltale signs of hacking, such as source routing or IP spoofing. Connections that exhibit these characteristics are dropped.
Sygate Personal Firewall
Free for personal use for Windows 95/98/ME/NT/2000/XP