The Perfect Linux Firewall Part I -- IPCop

From HowtoForge: The Perfect Linux Firewall Part I -- IPCop.

The IPCop project is a GNU/GPL project that offers an exceptional feature packed stand alone firewall to the internet community. Its comprehensive web interface, well documented administration guides, and its involved and helpful user/administrative mailing lists make users of any technical capacity feel at home. It goes far beyond a simple ipchains / netfilter implementation available in most Linux distributions and even the firewall feature sets of commercial competitors.