If you've ever need a digital servo but have balked at the price, the Open Servo Project should be an attractive option. The project seeks to develop software and hardware to replace the internals of standard servos like the Futaba S3003 and the Hitec-HS311.
OpenServo is an open community-based project started by Mike Thompson with the goal of creating a low-cost digital servo for robotics. The hardware and software design of the OpenServo is free for anyone to use and modify to meet their particular needs. It is currently being developed by a small group of dedicated individuals striving to maintain the very best in free, open source software and standards.
The project uses a 8bit AVR microcontroller, MOSFET h-bridge, "feedback of servo position, speed, voltage and power consumption", and only costs about $10 extra per servo (so, about $20 for one complete servo).
Visit the OpenServo Forums for more information.