I have had a couple of requests lately for some good reference materials for SBS 2003. MS Press has a couple of books that are decent --
If you really want to dig into SBS though, I would recommend picking up a few of the books by Harry Brelsford. He has been working with SBS since it's inception and knows SBS inside and out. You can get a listing of books by Harry on SBS over at his site --
One book by Harry that is not in his list but is excellent reading --
Small Business Server Start Kit -- Excellent if you are new to SBS
I have not read this book but I have seen a couple of promising reviews --
Also, a couple of SBS blogs to get subscribed to....