SmoothWall Express is a GNU/Linux distribution geared towards firewalling, with an installer, a web interface, and some common software like squid that can be useful when running a small business router. It is theoretically the basis for the corporate products of SmoothWall Ltd., who happen to employ me; but all opinions here are my own, and I'm not speaking for them.
Unfortunately, the SmoothWall Express kernel is somewhat "stable", which leads to problems installing the distro on modern hardware. There is a new version of Express in the works, but I'm afraid SmoothWall Ltd. currently has a bit of a "code dump" mentality with respect to delivering updates to their community, because they don't recall seeing any significant contributions from outsiders.
At DebConf I created proof-of-concept Debian packages of two components of Express 3.0: the swe3 web interface, and the smoothd daemon which executes privileged commands. Currently these can show a basic web interface; some of the less complicated bits will even run, and I can shut down my laptop using the "shutdown" button via smoothd. (Note that I still need to add boring stuff like debian/copyright files, but I plan to release these as soon as I can.)
In the near future, hopefully I can implement some of the more important features (like, er, firewalling), and add some other components like the traffic shaping and IM filtering daemon. I'm working towards a demonstration Debian Pure Blend that can show off some of the advantages of working with a third-party distribution as a base.
If anyone would like to help me... send me patches. :) I expect I'll be blogging my progress occasionally.