Consider yourself warned! It's Apple policy to phase out older routers in such a way that they are no longer usable. Case in point: I have two of the second generation Apple AirPort base stations, called "Dual Ethernet" in some places and "Snow" in others. (See the wikipedia page for more details). They work great, have wireless and wired access, let you use a dial-up connection or dial into them from your remote network, and do 802.11b perfectly. One was at my parents house for a while, another at my girlfriends.
Both are now at my house and I wanted to set them up for other things. First, I found this article on their factory default settings which led me to the one on how to reset the things so that I could reload the software. All seemed to make sense and sounded pretty straightforward. My only Mac is a MacBook Pro for work with the newest version of Mac OS X and AirPort utilities, so I seemed to meet all the requirements. However, the routers were not showing up in the Airport Admin Utility. Weird.
I search around about this problem and found many people with the same issue but no solution, and after digging around on Apple's website some more, I found this Airport Software Compatibility Table. So the "Dual Ethernet" router isn't supported in 10.4 or newer? That seemed strange. I downloaded the AirPort 4.2 for Mac installer, but running on Mac OS X 10.5 it claimed that it required "10.3.3 or newer." Last I checked, 10.5 was newer than 10.3 but *shrug*. I gave Apple tech support a call and after explaining the issue, I was told "Your cheapest option is going to just be buying new routers." WHAT? I have two perfectly fine routers that each cost $300 new, and it turns out Apple decided to just remove support for them from the configuration tool? Wow.
So I dug around some more. I remembered using Windows to configure them at one point so I booted up Windows XP on the MacBook Pro and searched out the older software. It is still available here: AirPort 4.1 Download for Windows and will allow you to configure your older Apple routers. However, this isn't feasible for me because I don't typically have a Windows installation that I can get to for the planned uses of these routers, so they're now for sale. Check Craigslist, Facebook, or event comment here if you want them. Sold to any reasonable offer. These things work great and are only limited by Apple removing functionality from new versions of their software and not providing a downgrade path (Older versions of OS X won't install on these x86 laptops). Even though I recently got a new AirPort 802.11n router (that also works great) I will not be buying another piece of Apple networking hardware.
(Also, I had lots of phone line problems and ended up switching from Speakeasy Business DSL to Comcast Business Cable. I've had to deal with Comcast on the phone once already and their support system is a complete mess, but for the same $ I'm getting my static IP and 15Mb download/2Mb upload instead of the 1.5Mb download/384kb upload.)