www.smoothwall.org

A secure operating system that converts a redundant PC into a firewall and VPN gateway. It is webmanaged so no keyboard, monitor, or mouse on the device is needed. It supports Internal ISDN, all popular NICs, all popular connection types (Modem / ISDN / Cable / ADSL / USB ADSL / Ethernet) and also features a fully logging firewall, DHCP server, IPSEC VPN.