I agree there should be a "lets Build A Nixie Clock"
oh eerr... I didnt mean to start being a teacher.
But if, hypothetically, somebody wanted to build a similar one, then they'd start with...
1. An Arduino board. http://arduino.cc/en/Main/Hardware
I think mine was a Uno, or at least a copy thereof, as bought on Ebay.
This is the brains of the machine.
2. An ArduiNIX "shield" board.http://arduinix.com/index.html
This board provides a simple interface between the Arduino board and the nixie tubes.
Not in a physical sense, but rather to control the voltages required. The nixie tubes need about 180 volts to run, and this board does that job.
The Arduino programs to suit it can be found at this site also.
3. A power supply.
I built my own. A simple analog mains to 9 volts job, using a transformer, rectifier diodes and 7809 regulator in the standard manner.
If you dont know what I just typed, dont build one but use a commercially built "wall wart" 9 volt supply instead.
4. Nixie tubes.
Nobody makes these anymore, but you can get used second hand ones from various places on the net.
I got my "IN-8" tubes, and also sockets for them, from this ebay store...http://stores.ebay.com.au/Vintage-Electronics-and-Tubes
5. Assorted hardware you'll have to do yourself, such as the box and so forth.
The wiring from the tubes (44 pins in total) to the ArduiNIX board (24 pins in total) is rather complex. Its multiplexed, and although described at the ArduiNIX site is still a hell of a job to all wire up by hand.
As an alternative, you could use a prebuilt board from them which suits "IN-17" tubes instead.
Its all personal preference.