I have been working on an exhibition called 1001 inventions for the past few weeks. It is opening at the science museum on 21 Jan 10 (I think).
I managed to use 8 Arduino pro minis for simple led lighting and sound displays in different exhibits.
For the elephant clock (below), I ran out of pins, so I had to change to a mega644 chip but all the software was developed using the Arduino libraries and IDE.
This link http://tinyurl.com/yftemkp shows a few (not very good) pictures of the clock. Unfortunately I did not have time to get a video of the half hourly alarm cycle because the BBC arrived on site and I was unceremoniously hidden out of sight while the press interviews were taking place.
There is a video on youtube http://www.youtube.com/watch?v=9Ue7GNRz0Y0 which gives a good explanation of what the clock does and it is much easier to see this than try and explain it all in words.
The original clock was powered by water but the one in the museum has 5 dc motors to drive the different figures ( the phoenix on the very top, Saladin sat on the platform at the top, one in each dragon and one in the mahout) as well as two stepper motors to drive the time display parts of the clock.
The timekeeping is done by a DS1307 chip which communicates via i2c with the 644 chip, this then acts as a clock source for the stepper motors and also switches relays on and off to control the dc motors.
There will probably be a small mention of this on the London news programs on 21 Jan about 6 - 6.30 in the evening.
If I get a chance I will try and get a video of it in operation.