From Curtis Jones:
GlowWorm FW Lite is a rule-based network security and monitoring application built on plugin-accessible framework.
Rules can be defined on the basis of a set of connection criteria include the addresses, ports, relevant endpoint and protocol. Additionally, rules can be restricted to a particular set of users, groups or applications, and the lifetime of a rule can be limited by the lifetime of that application or until the machine reboots.
Relative Network Names allow one to specify symbolic endpoint address like localhost, localnet or remotenet instead of having to "hard code" an ip subnet address.
Rule Actions can alert you using a user-customizable dialog message (based on an sprintf-like format so that you can choose what information to include), if a particular rule matches.
Support for incoming and listener connections provides a more precise means of controlling network traffic than offered by the Mac OS X Firewall.
Drag-and-drop rule re-ordering makes prioritizing rules an intuitive and easy process.