While you're at it, I would highly, highly, highly recommend a book on Refactoring code as well. Design Patterns and Refactoring really go hand in hand. The Refactoring book is a must have on any Java bookshelf, and it's an easy read as well:
I second the recommendation for "Refactoring" - after I read that, I had a much better understanding of how the patterns help.
Another good book on design in general is "Agile Software Development - Principles, Patterns and Practices".
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
Though some OO purists may not fsvor some of the examples in the book !
Joined: Jan 29, 2003
Google for "THinking in Patterns". It's by Bruce Eckell who did "Thinking in Java". I think it's free online at his site. It covers GoF with Java examples, but at a quick glance I didn't think it added much more.