This week's shameless plug comes from InfoWorld:
Put your router/firewall on steroids by installing packages like nmap (network security scanner), snort (intrusion detection), and tcpdump (packet sniffer). Together with iptables (which comes with the Linux kernel), you can turn your OpenWRT box into a powerful security tool. Install openvpn, and you have a very affordable VPN device. And if it strikes your fancy, you can install quagga and turn your dusty little Linksys into an OSPF and BGP-capable router.
Full article here