I've been wanting to do something with Nixie tubes for some time now, and managed to find a few while rummaging through some old electronics a friend gave me a couple years back. After some research and a little testing here's my findings for those just getting into them:
*They're powered by 180ish volts DC and very low amperage
*They're fairly forgiving on what voltage they're fed. I got them lit with as little as 120vdc and as much as 200vdc without burnout.
*nixie clock kits are about 75-200 dollars depending on the kit without tubes.
*there are single and dual anode tubes, mine are dual anode, most kits only work with single anode
*I probably had enough stuff around the house to get one at least lit up to test!
So here's how I went about it!
Step 1: Materials
1ea - nixie tube (single or dual anode, look up your tube's pinout.)
1ea - tube socket (optional, but makes life easier)
1ea - 12v dc CFL lamp (normal household CFLs won't work)
4ea - 1D2 diodes (for bridge rectifier)
1ea - 22k ohm resistor (for current suppression)
1ea - 3v lithium battery (other power sources around 3-4vdc may work fine as well)
wire and solder to connect components (duh)
Step 2: Extract CFL Driver Board
Since our Nixie tube need high voltage to light up we'll use the CFL's HV circuit to save the legwork of converting the battery's 3v to something closer to what the nixie wants. This step isn't too hard, but be careful not to break the tube of the CFL. Open the casing for your CFL, clip the wires from the 12v screw in socket and the two high voltage ac wires to the lamp tube, making sure to note which went were.
Step 3: The Basic Circuit
While this could be done in a much cleaner layout, the photo at the end shows that this circuit can be done quite simply. Twist the diodes into a bridge rectifier as shown in the diagram and solder it's positive DC end to the 22k resistor, then solder the rectifier to the HV ac output wires from the driver board. next attach the HV DC negative to your number of choice (I like 6), and and the HV DC + (the end of the resistor) to the anode of the tube. Lastly hook up the driver's power lines where they originally attached to the screw-plug of the lamp housing and it should light up! Be mindful though, since now you have high voltage AC and DC in this circuit. It'll bite if you're not careful with it.
Normally the driver board needs in the neighborhood of 400-1500 volts to power it's CFL tube, but since it's expecting 12v for a power supply, when you feed it 3v instead it outputs closer to 140vac, then our bridge rectifier does a dirty but serviceable AC-DC conversion and the tube is made happy.
Step 4: Making Something Nicer
Once I had the basic circuit design down, I added onto it and came up with this phone number display. Each tube's anode needs a separate resistor and I added another battery since the voltage dropped to about 75vdc when they were all on one battery. The whole thing is mounted into a small wooden box and a small anatomical model shows the whole thing off.