I picked up a few GU128x32-311 vacuum display modules (VFDs) on ebay. These are graphic/character displays, and fairly easy to interface with. I figured that they'd make a nice animated clock. The design is an analog clock face on the left, a graphic of the phase of the moon on the right, and the time/date in text in the middle. Since I had a line to spare, I created some 5x7 rune fonts and display the time in them also.
The VFD needs only a 5V power source, making htis a fairly easy clock to build. I use a MAX1302 RTC chip with a backup capacitor, a DS32khz temperature-adjusted oscillator (accurate to 1 minute/year), a quantum research QT110 touch sensor for a button, and a rotary encoder as peripherals to a ATMEGA32 microcontroller. The only problem I encountered is that the GU128x32-311 has a slow refresh, so redrawing the entire screen each second leads to a lot of flicker. Instead, I redraw only the second counters each second, and the entire screen each minute.
I made another clock for a friend, mounted in a L-shaped piece of lucite I found in a pastics store on Canal street.
I sent a programmed microcontroller to Sture Nystrom, who made the clock below.
The moon phase data is here, and the moon phase lookup code is here.