I used Zonealarm until recently when I tried the free version of Sygate. I find that Sygate is geared towards the more knowledgable computer users. While both work, as does Norton's firewall, I like the logs that Sygate produces and the automatic shutoff to IP addresses that are scanning your system. Also, as an added plus, the program does a great job in catching worms before they can do any damage (and before they can be caught by Norton AV). There is a computer security web page that was in my list of favorites. I tried to access it, and was immediately notified by Sygate that the Nimda worm was attempting to access my system. Sygate quickly shutdown access to the site.

Just a thought -- if all computer users had Sygate, then the Nimda worm probably wouldn't have spread as much as it did.