Everything you ever wanted to know about SQL Server 2005 is contained in Books Online (BOL). I think it's the best Microsoft server documentation that we've ever produced. And guess what? It just keeps getting better! :-). Make sure you download the latest update we just released at:-
Download SQL Server 2005 Books Online
Oh, and why should you download it? Well, how about you Oracle DBA's out there that want to know can SQL do this or do that... download BOL and search it. It'll soon tell you.
What about you SQL Server 2000 DBA's out there worried about migration to SQL Server 2005 and what new features you might take advantage of... download BOL and search your worries away. ;-)