Two new whitepapers from the SQL Storage Team:

 

Working with TempDB
http://download.microsoft.com/download/4/f/8/4f8f2dc9-a9a7-4b68-98cb-163482c95e0b/WorkingWithTempDB.doc
 
Physical Database Storage
http://download.microsoft.com/download/4/f/8/4f8f2dc9-a9a7-4b68-98cb-163482c95e0b/PhysDBStor.doc