There are graphical and web based interfaces being developed to work with the Linux filtering rules. Some companies have even create commercial firewalls based on Linux by putting it in their own box with their own management code. (nice)
gfcc (GTK+ Firewall Control Center) is a GTK+ application which can control Linux firewall policies and rules, based on ipchains package. Go to http://icarus.autostock.co.kr and get your copy.
kfirewall is a GUI frontend for ipchains or ipfwadm (depending on your kernel version). http://megaman.ypsilonia.net/kfirewall/
FCT is an HTML based tool for the configuration of a firewall. It features automatic script-generation for IP-filtering commands (ipfwadm) on a firewall for multiple interfaces and any internet services. http://www.fen.baynet.de/~ft114/FCT/firewall.htm