Free Personal Firewalls
WIPFW is a MS Windows operable version of IPFW for FreeBSD OS. You can use the same functionality and configure it as you work with IPFW. There are two related parts to ipfw. The firewall section performs packet filtering. There is also an IP accounting section which tracks usage of the router, based on rules similar to those used in the firewall section.
Excellent free firewall for windows that is free for personal use.
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).
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.
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.
This is a free firewall for Windows 2000/XP/2003 from Comodo. You have to supply an email and use the activation code they send you within 30 days to keep using it. However, according to Comodo, it is a 'lifetime' license for free.
Filseclab Personal Firewall Professional Edition
This is a free Windows firewall that is compatible with Windows 95/NT/98/ME/2000/XP/2003.
GhostWall is a personal firewall for Windows XP/2000/2003/XP64 that is designed to replace the default firewall that comes with Windows.