DD-WRT is free Linux-based firmware for several wireless routers, most notably the Linksys WRT54G.

Tomato is a small, lean and simple replacement firmware for Linksys' WRT54G/GL/GS, Buffalo WHR-G54S/WHR-HP-G54 and other Broadcom-based routers.

Untangle wins a network security solution.

IPCop is a Linux distribution which aims to provide a simple-to-manage firewall appliance based on PC hardware.

OpenWrt is an embedded operating system based on Linux, primarily used on embedded devices to route network traffic.

Wicd (Wireless Interface Connection Daemon) is an open source software utility to manage both wireless and wired networks for Linux.

Endian Firewall Community is an Open Source Firewall and UTM Appliance with offers unique usability and features.

Smoothwall is an Open Source free firewall that includes its own security-hardened GNU/Linux operating system and an easy-to-use web interface.