Information Modeling and Relational Databases by Terry Halpin
This is the definitive text on the subject of Object-Role Modeling (ORM) and a book that should be read by every data modeler/database architect. If that isnt enough praise for you, you can read more in my
review.
Data Model Patterns: Conventions of Thought by David Hay
This is one of the most cited data model
patterns books out there... and for good reason. I may
not always use the models exactly as they are in the
text, but I reference them constantly.
The Data Model Resource Book by Len Silverston
Another data model pattern book I reference
constantly.
Analysis Patterns by Martin Fowler
"OO Guys" have something to say about data
model patterns too. This is the other patterns book
I refer to a lot.