Nice article. I whimped out and bought one all assembled and running Linux with one interface attached to a builtin 4 port switch, a second interface for the public side and the 3rd wireless interface for the wireless clients. It is capable of routing, bridging, etc. It can also be modified, I actually installed and ran a copy of Snort on it for a while. That is, until I killed it by uploading one of my custom firmwares that wouldn't boot, and not having followed a certain procedure to allow me a way back out of the problem. But heck, at $70 it's hard to beat. It also gives you 802.11G in addition to 802.11B support. It's a LinkSys WRT54G:
http://www.batbox.org/wrt54g-linux.html
Now, building your own would certainly allow you to overcome some of the shortcomings of the LinkSys unit. Having more memory available is the primary thing the WRT54G lacks which limits what you can do with it. That and you have limited processing power with the little MIPS processor (showed less than 100 Bogomips on my unit, before I killed it). I was thinking of driving down to Best Buy this afternoon to see if I can find a replacement. I ordered the last one off of Amazon. I wouldn't mind building my own but I don't have the hardware lying around. I was thinking about just adding a wireless interface to my existing Linux firewall box though. It already has 3 interfaces and not sure if I have room for another (it's a really old Pentium 100).