When I saw Jason McDonald's design patterns quick reference guide I marked out. I forwarded the link to everyone I knew who heard of the Gang of Four and printed out a nice, one-page color version to keep. I almost freakin' framed it. I liked how succinct it is... it gives you the class diagrams so your brain is instantly sparked, and just enough description that you still have to think analytically about the pattern.
A few people asked me about the original Design Patterns book and a few others mentioned how much they liked Head First Design Patterns. I have to sadly admit - I originally wrote off the Head First series as just another "X for Dummies" clone, but now that I read the RMI section of their Java book and read the first 100 pages of their Design Patterns book I have to admit I judged... sigh... a book by its cover.
The RMI section was actually fairly straight forward and illustrative and even included an informative chapter that included Jini. The Design Patterns book has done a good job of explaining the Decorator pattern, something that I can't do with a pencil and paper in front of someone. Both books have been good references for me to pass along to other developers.
If only there was a pattern to remove outdated cliches two paragraphs ago.