Fwbuilder was one of three GTK applications I used (inkscape and gimp are the other two).
And today I noticed that version 2 is Qt-based :-)
I like it a lot. In fact, as I say in my classes, it's the first firewall configuration application for Linux I've found that is actually easier than editing a script, since almost every other one I've found is a glorified rule editor.
Bonus cool application: p3scan
I found about this today, when a customer asked me for a way to viruscan his incoming mail. Which is stored in a bunch of accounts all over the internet :-)
For webmails, a squid redirector does the job, but for pop3? p3scan is completely transparent (only requires a tiny configuration and a NAT rule) and for what I tested it, works just fine.
I am using it along with clamav, but it also supports Kaspersky, F-Prot, and almost anything, really.
Cool gadget, and it's just a 72KB download.