T.M.
My daughter was 2 when her brother was born. Before he arrived, we read What Can Our New Baby Do? by Joan Holub. It's very funny and even she could understand the humor. We would make jokes and references to it after he was born. Like, "he can't eat polar bears! What does he eat?" These jokes would diffuse jealousy when I was breastfeeding.
The other book we love is I'm a Big Sister by Joanna Cole. We read this after he arrived. We make references to it all the time. She loves this book and pretty much has it memorized. So my 2-year old highly recommends these books!
One more idea - since they probably won't let your daughter in to the hospital to see the baby, take pictures of him and have someone upload them to your computer at home so she can watch a slideshow of him. Also, a friend of mine printed out some of the pictures and laminated them so my 2 year old could have her own pictures of her brother. Seeing/having pictures of her brother got her really excited about him.