For those interested in reproducing my biNixie Clock, here is the (most likely) schematic diagram:
I have realized I did not take notes while building it, probably because it is so straightforward (and a copy of other designs).
You need to pay attention to the current limiting resistor (one per Nixie tube), which depends on the tube model and your anode voltage ("HV" in the diagram).
Put everything on sockets so it can be easily replaced or reused.
At current prices (3/2016) the whole thing should cost less than 30 Euro if you use common Nixies like B5092/ZM1020.
The firmware for Arduino and compatible boards (ATmega368) is here https://github.com/jh1995/biNixieClock.
Please share pictures of your biNixie clock as well as firmware improvements!