Nixie displays are the old tube-based displays that were widely used in electronics back in the 1960s to display numerals and symbols. Their retro style is what makes them attractive to do-it-yourselfers now.
Here's a huge gallery of all kinds of nixie clocks made by people all over the world. Some of them look cool, but some of them look really cool. You can find loads of these pre-made ones on eBay, but we wish they sold them in stores we could pick one up for our nightstands.
Nixie Clock gallery [Electric Stuff]