When my siblings and I were very young we lived in Japan for a few years. Dad was in the Air Force and was stationed there. Since it was impractical for Grandma to come visit us, she recorded herself reading children's books and mailed us tapes.
Almost every night we'd pop in one of Grandma's tapes and fall asleep to her comforting voice reading Dr. Seuss or something, and then she didn't feel so far away. I don't remember what my favorite was, or if I had a favorite, but I do remember how much I enjoyed getting to hear her voice every night as I drifted off to sleep.