OPNsense!

pfSense is a free, open source customized distribution of FreeBSD tailored for use as a firewall, and router. In addition to being a powerful, flexible firewalling and routing platform, it includes a long list of related features and a package system allowing further expandability without adding bloat and potential security vulnerabilities to the base distribution, making it a fully qualified UTM device. pfSense is a popular project with more than 1 million downloads since its inception, and proven in countless installations ranging from small home networks protecting a PC and an Xbox to large corporations, universities and other organizations protecting thousands of network devices. »

IPFire is a server distribution with intended to use as a firewall. It focuses on flexibility, and scales from small to middle sized business networks and home networks.

Zeroshell is a Linux distribution for servers and embedded devices aimed at providing the main network services a LAN requires. It is available in the form of Live CD or Compact Flash image and you can configure and administer it using your web browser.

Untangle is a platform for deploying network based applications. The platform unites these applications around a common GUI, database and reporting. Applications on the Untangle platform inspect network traffic simultaneously, which greatly reduces the resource requirements of each individual application. Untangle can act as a complete unified threat management (UTM) box, going beyond just a basic firewall or router. It's aimed at small-to-medium businesses and enthusiast home users. It runs in line as a network gateway, so it allows control of all devices connecting to the network. Untangle offers a free, open source Lite Package as well as a full-featured, commercial Premium Package. Untangle has about 40,000 installations worldwide protecting over 2 million people in businesses, schools and other organizations. »

IPCop Firewall is a Linux firewall distribution geared towards home and SOHO (Small Office/Home Office) users. The IPCop interface is very user-friendly and task-based. IPCop offers the critical functionality of an expensive network appliance using stock, or even obsolete, hardware and OpenSource Software.

Endian Firewall Community (EFW) is a "turn-key" linux security distribution that turns every system into a full featured security appliance with Unified Threat Management (UTM) functionality. The software has been designed with "usability in mind" and is very easy to install, use and manage, without losing its flexibility.

The SmoothWall Open Source Project was set up to develop and maintain SmoothWall Express - a Free firewall that includes its own security-hardened GNU/Linux operating system and an easy-to-use web interface.