Nixie tubes - the displays from the previous century. Although they can be considered as hopelessly out of date, and somewhat tricky to drive - they're having a resurgence in popularity especially with the DIY crowd. One example of this is by Australian Arduino forum member 'randyrob' who has used ex-Soviet IN-12 numeric tubes and an Arduino-compatible to create a clock from the past. The clock is operational however the housing is a work-in-progress - for example:
However building such a clock is rewarding, and it's nice to watch the digits glow - soclick here for complete details and notes. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
When making your own clock - don't skimp on timing accuracy - so consider using our real-time clock module based on the DS3232 - with a temperature-controlled oscillator it is highly accurate, and has an onboard backup battery for when the power dies and 236 bytes of non-volatile memory for user data.