At some point I expanded the standard Servo library so that there's also a method to move servos at reduced speed.
Korman, I'd like to see the Servo with Speed Control library for another application. Is it online?? Thanks.
@aukio, if you need variable slow speed, perhaps with acceleration/deceleration, you may want to consider stepper motors. Uses more pins, though: 2 or 4 per motor. I have some small, cheap ones with driver boards. A tutorial is here: http://arduino-info.wikispaces.com/SmallSteppers
and more general information about Stepper Motors here: http://arduino-info.wikispaces.com/StepperMotors
DISCLAIMER: I mentioned stuff from my own Shop...