Servos have three pins: Power supply +, Signal and Ground.
Basically, you supply pulses to the signal pin and the Width of the pulse determines the servo position. However, you need to continually supply these pulses....
Think they are a couple of options:
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Connect all the servos to the one PWM output (via a buffer) and switch the power to the servo you want to move. Move the servo, move the servo then power it down. Trouble is, if there is a force on the servo, it won't maintain the position.
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Take a look at this board: https://www.sparkfun.com/products/10615
This has 16 PWM outputs - one going to the signal of each servo.... which should be enough in conjunction with a hefty power supply (Maybe use a Desktop Computer power supply). Just make sure you link the ground of the power supply to the ground of the Arduino boards.
Have fun.
Andrew.