I found this great post over on Pantz and I have NO idea who the author is. Its a really handy init script for setting up iptables for a laptop. There are a couple lines there that you can uncomment if you want to open up ports 22 for SSH or 21 for FTP. Of course, you could just copy those lines and substitute the port number for anything else if you want to run something else.

What you need to do with this script is copy/paste it as root in /etc/init.d somewhere, I named mine firewall.sh and chmod 755'd it.

Get it here.

BTW, if you wrote this or know who did, let me know and I'll credit and thank you.