I have been a huge fan of Baba Yaga since the appearance of her Dancing Hut in Dragon magazine years ago. I've collected every version since.
Allow me to recommend Baba Yaga:The First Setting in Rassiya. It was written by Michael Fiegel and published by the good folks at Dog Soul. It also won a gold ENnie a little over a month ago. It is an excellent supplement and certainly deserved the award.