Firelet – distributed firewall management (opens in new tab)

For an analogous tool, see http://shorewall.net/Shorewall-Lite.html - text configuration files instead of web UI. Also, Shorewall is much more mature - although I don't know if the Shorewall-lite distributed configuration is as bulletproof as single-host Shorewall is.

This site is blocked by my work firewall for being a "proxy." I am amused.