WotC has put up the 4e stats of Baba Yaga, the Hungry Witch, up. You will need DDi access.
Baba Yaga has been part of the D&D universe since the beginning. Eldritch Wizardry and the DMG featured stats for her Dancing Hut and there have been adventures to feature her over the years as well. The great D&D witch Iggwilv is said to have been one of her students.
It's a good article. Reading it I do notice that WotC falls into the trap we all do, making any mythical NPC just really, really powerful; she is a 27th level opponent here.
I think I should stat her up for "The Witch" and see if I can get by with less level, but still give her the power she needs.
ETA: The oddest thing just occurred. I was reading my post in Google Reader with auto translate on, and it changed "Baba Yaga" to "Father Nyaga". I think I need to come up with a male witch that is Baba Yaga's counterpart, or enemy or something. Maybe he is a wizard and thousands of years ago, so long that even he and Baba Yaga were young, they were lovers. I like that idea.