When I was setting up my first home linux firewall box I loved reading this tutorial:
Linux 2.4 stateful firewall design
http://www-106.ibm.com/developerworks/linux/edu/l-dw-linuxfw-i.htmlHere I learnt how to do portforwarding (NAT) to services within my LAN:
Linux 2.4 NAT HOWTO
http://www.netfilter.org/unreliable-guides/NAT-HOWTO/index.html
Red Hat Linux 6.X as an Internet Gateway for a Home Network
http://en.tldp.org/HOWTO/mini/Home-Network-mini-HOWTO.html
was also helpful, though I used iptables instead of ipchains.
