YpFw is a frontend to ipfw and dummynet. It was developed to ease the setting and managing of ipfw rules and dummynet pipes on FreeBSD. It features a curses text interface, which allows the user to add/delete rules, update/clear rules counters, and add/delete/configure pipes. It is not meant as a replacement to ipfw; the user will need to understand ipfw and dummynet rules and syntax.
Amber sits in the tcpserver chain for qmail and implements an "amber list" for incoming mail. This neither accepts nor rejects connections, but implements a number of timing-related tricks to fake out spam and virus software that doesn't implement SMTP correctly. For example, it can defer requests from new IP addresses for a few minutes before it starts passing connections on to smtpd, pause and check for programs that send data before the HELO, and otherwise make things rough for bandit bulk mailers.
Lokiwall is a firewall script for Linux. In addition to the standard function of easily limiting network traffic, it features dual routing (using two Internet connections simultaniously), connection fail-over, load balancing, traffic control, advanced masquerading, advanced DNAT, and advanced marking (to direct specific traffic to a certain interface). The advanced features require some kernel patches. The standard features will work on a default Linux system with iptables and iproute2.