Saw this on the Gear Diary blog. Apparently Zone Alarm is celebrating their 15th birthday by giving away a copy of Zone Alarm Pro between 11/18/08 - ends 11/19/08 6AM PST. You send them your e-mail and they will send you a reply with a unique key to activate on one computer. I sent my e-mail, but the web page stated due to heavy traffic a key will be sent within 48 hours.
Direct link to offer: LINK
Personally, I use Comodo's free firewall v 2.4, but I guess I'll try this out.