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 --

Small Business Server 2003 Administrator's Companion

Small Business Server 2003 R2 Administrator's Companion

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 --

http://www.smbnation.com/smb%20books.htm

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 --

How to Cheat at managing Microsoft Small Business Server 2003

 

Also, a couple of SBS blogs to get subscribed to....

The Official SBS Blog (Microsoft)

EBitz - Susan Bradley (SBS Diva!)

 

Cheers!