Ebook: Beginning Database Design Solutions (Wrox Programmer to Programmer)

Definitely the best database design book I've come across. A great mix of theory and practicality that will leave you well-prepared to tackle just about any design challenge. The best part about the book is that it's not specifically tied to any database, it's more about the principles and guidelines that you will use in any implementation, but without the overbearing academic vibe. I was a little worried when I opened the book and saw that he was an MIT nerd, but the author is quite a character and does a great job talking to those of us on planet earth.

Well written, tons of practical advice, plenty of subtle humor, and very easy to read. There are loads of examples, exercises, and real world tips that keep this (normally dull) topic interesting. Bravo.