STK200 compatible programmer
Presented here is a simple schematic for programming the AVR on the OpenServo.
"http://elm-chan.org/works/avrx/report_e.html" A fantastic site detailing hardware programming interfaces for many MCU components.
If you don't own an STK500 or similar programming interface, this one will suffice. It is a generic AVR programmer so it should work for other projects too.
For a compatible Windows/Linux flash software, see AVRDude Bootstrap guide