Normally to drive a servo from an Arduino you use a digital pin for each servo (plus 5V and GND). However using a method and Arduino library published at the RC Arduino blog, you can control up to ten servos using only two digital I/O pins and an external 4017 logic IC. It's much easier than you think, and really saves on I/O pins. The only warning to heed is that you don't exceed the current ability of your Arduino, and therefore power the servos separately.
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