Software to run on an Arduino to control servos and interact with other boards on an I2C bus
Details on the code here:
Details on wiring, mounting servos, etc. here:
http://www.prestonanddistrictmrs.org.uk/articles/point-control-with-servos/
This project is now dead. I decided the arduino was just not fast enough for what I wanted, so moved to Raspberry Pi, with the added advantage of a GUI for trouble-shooting. See here.