... don't overlook IPCop either - a branch off from Smoothwall or the otherway around and another dedicated firewall linux distro.

I have it running here to protect the home network, runs squid, snort, and traffic shaping - not a bad package at all in a 40mb iso. Content filtering via Dansguardian is also available through an addon package, but requires a bit more RAM to keep it all running nice.

Like Smoothwall - it takes around 10 minutes to install - so if you break it by over tweaking - no real harm done, 10 minutes or less and your back up and running.