There have been some questions lately about Gateway/Router/Firewall computers. I just had to try this one out:http://www.untangle.com/
Looks like it's Knoppix based, with heavy use of Java. The hardware requirements are high (Think XP), but that muscle seems to be put to good use.
Installation and setup is very easy. It gives you plenty of warning, but in the end your computer will be a dedicated special purpose appliance. The interface is all point and click, and worked out of the box for me. It's probably way overkill for most home users, but I think I'll keep it as a bridge between my network and a test computer for a while to see how it does.
The company says "95% of their product is open source". Not sure what the remaining 5% are, but the free package is extensive.
You have to supply some information (but no verification or call-back) during setup. After install it shows an "Activation Key" in a summary page.