I wrote a servo controlling program for the AVR Minimus. It can control up to three servo motors given commands over a virtual serial port (over the USB connector).
It's based on an example program from the LUFA library (http://www.fourwalledcubicle.com/LUFA.php). LUFA is necessary for the virtual serial communications - doing the actual servo signals is pretty easy.
There are more details on the github page: https://github.com/jmacarthur/minimus-servo
Don't do what I did and power a servo motor directly from the Minimus - I don't know how much power a servo draws, but it's probably more than the USB port should supply.