Untangle
For small networks, I recently became aware of a new firewall/web filter option for Linux, it's called
Untangle.
What I love most about this product, is although it's based on Linux, it's a cinch to setup, and administration is a breeze. It has many features like Snort you want on your gateway, in a standard format suitable for most very small networks, but in the past always required a lot of manual Linux config file editing and command line work to setup and maintain.
There are other software appliances for Linux, but few inexpensive ones have good as a user interface. And fewer still provide web filtering and a decent block list, and software updates out of the box, for free.
For 90% of small networks, pfSense, or Untangle will be great. The free version is nothing to sneeze at.
Untangle have some professional options, commercial addons, for advanced policy config, which are downright cheap, compared to competitors like Smoothwall. We're talking prices on the order of $50 a month or so, for 50 users.
When prices like annual $1000 or so are common, for a tenth the number of features available.
Needless to say, i'm very impressed.