Comodo Personal Firwall Pro is a free firewall with a lot of options (a lot of more than Jetico Firewall free), that can be deeply configured. In my tests it has reached very good results even with the default configuration.
The graphical user interface is beautiful, better tan most of its shareware competitors, and indeed, since the number

of options and potentialities, it seems completely a shareware firewall. In comparison to Jetico, it asks for many more updatings, which can be a positive or negative thing according to the points of view.
The result in the firewall test of December 2007, has been of absolute excellence.
The version 3.0 add an anti intrusions system (HIPS) respect to the preceding 2.4 (version that in effects I liked a lot it). We will see how it will evolve him in the future.

In this moment, I consider Comodo Personal Firewall Pro the best free firewall.