I'm not sure if this is the correct category but since the Projects-section of this forum is not allowed to be used for such posts, I try it here:
At http://sourceforge.net/projects/tardyondrive-avr/ there is a complete implementation and documentation of an ATTiny-based stepper motor controller available. This includes hardware design (schematics), firmware that runs on the AVR, host-side client library that communicates with the controller and provides programming interface and a few example applications.
This controller can be used to move a stepper motor, it emits a direction signal and step-pulses for movement. It of course needs a power driver for the motor itself but full logic of controller (including acceleration/deceleration, referencing, external triggering of movements) is done on the ATTiny.
All sources and hardware layout are available for free. Comments, ideas and suggestions are welcome - but it would be best they arrive as patches to the sources provided at http://sourceforge.net/p/tardyondrive-avr/code/ci/master/tree/ ;-)
*Moved by moderator*