Hm, I've introduced Ruby programming to a couple of non-programmers and thought the book "Learn To Program" by Chris Pine was good. It doesn't assume much and starts from the beginning. It's very hands-on, ie, not much theory, but if there's someone available to answer the inevitable questions I thought it worked pretty well (50% success rate).

Good luck! I love teaching if the person is genuinely motivated, it's really rewarding and you end up feeling you understand the subject better yourself just from having to explain it.