Take a gander at http://openservo.com/
OpenServo is an open community-based project with the goal of creating a high quality digital servo for robotics.
Some of the many features of the OpenServo include:
- High performance AVR 8-bit microcontroller
- Compact H-Bridge with high performance MOSFETs
- Precision control over servo position and speed
- I2C/TWI based interface for control and feedback
- Feedback of position, speed, voltage and power
- Advanced curve based motion profile support
- EEPROM storage of servo configuration information
- Software written in C using free development tools
- I2C/TWI bootloader and GUI programmer