How about a software which lets you build your own firewall ?
One of my reader recently mailed me asking if there was any firewall which could support multiple ISPs for Internet connections. The best solution I can suggest is Firewall Builder. It gets better if your are on Linux as you get the complete package free, else for windows/mac you’ll need to pay some license.
It is one of the best configuration and management tool, and what gives it more advantage is that it has a GUI, making it all the more easy for folks who can’t deal with shells and command consoles. It supports iptables (netfilter), ipfilter, pf, ipfw, Cisco PIX (FWSM, ASA) and Cisco routers extended access lists. If you are an administrator then it makes your life very simple. You can maintain a database of network objects, edit policies all using simple drag-and-drop operations.
If you are on Linux, you get Firewall builder completely free where as if you are on windows, you can download a 30 day evaluation pack which can be renewed at the end of 30 days or later.
[ Download for Mac OS X (Tiger and Leopard, Intel) ]