A 'nixie' is similar to a tube (the things they used as 'transistors' before sillicon transistors existed -- my boss at the university worked on the first Dutch computer, and he had a 'bit' lying on his desk, the thing was huge), but it uses less current and doesn't need to to 'warm up'. It's like a little neon tube: the symbols are all small wires that you run >150 Volt through. The neon gas around the wires starts to react, producing a steady, warm glow.
My first sight of a nixie were the huge nixies at the Evoluon that were used to count the number of visitors.
The things were made until the mid-70's, but as LEDs and (later) LCD became popular, they have been discontinued.
Nixies were doomed to be a forgotten technology, a product of ingenuity that was carelessly discarded as easier technologies became available -- like a small child discards an old toy when it gets a new one.
But not everyone forgot the nixies. As the equipment that used them was being replaced by newer equipment that utilised LED and LCD, the nixie tubes became available cheaply. And of course, the electronics hobbyists, who had fond memories of the things, snapped up those bargains. A lively trade in nixies sprang up, as people used them in their own projects.
Nixies are praised for their nostalgic qualities and their warm glow. Perfect for something like a clock.
About a year ago, I almost bought a nixie clock kit -- unfortunately the organiser canceled the whole deal. But yesterday, someone pointed out KWTubes, an Ebay-shop based in Latvia, that deals in Russian Nixies. 10 dollars for a set of 6 nixies isn't too much, and I now know enough about electronics to be able to design a driver circuit that has the features I want (helped, of course, by the nixie clock schematics on the internet).
But the power supply is a bit intimidating: it needs high voltages, and I haven't worked with anything >5V yet. The text accompanying the schematics is also not very reassuring -- messages like "OMFG, if you touch this part of the circuit while it's connected to the mains, you'll die!" abound...
Perhaps when I have finished some other projects first. I know for a fact that klik's parents would appreciate a nixie clock in a decorative wooden case...