Nailwall is a IP packet filtering firewall and net gateway (NAT) system for Linux systems running kernel 2.4. Its based on Monmotha's popular IPTables firewall with a few changes which make it much more pleasant to use on a Red Hat system.
Basically I was tired of firewall scripts which were functional from a purely technical point of view but completely screwed up from an administration / maintenance perspective. They use non standard initscripts (or no initscripts at all, jumble config info in with executing code, don't deal gracefully with problems and conflicts with other software, and aren't packaged, requiring nonstandard mechanism to install, query, upgrade, and uninstall. So I took one of the best firewall scripts and spent a little while fixing it. Here's the changes:

• Runs as a service, and uses a standard SysV init script which supports all the usual arguments (start, stop, status, restart, plus a paranoia setting which disables all networking completely)
• Seperates configuration information from the actual iptables commands.
• Coexists much better with other packet filter services
• Is packaged
• Is documented
• Handles failure gracefully