On the Zend Developer Zone there's a new article from Keith Casey where he talks about some of his favorite design patterns he's come across in his time as a developer - adapter, facade and decorator.
Within the Design Patterns world, there are four main categories: Architectural, Structural, Creational, and Behavioral. Architectural patterns describe the system as a whole, Structural patterns describe the relationships between objects, Creational handle creating objects, and finally Behavioral describe the communication patterns between objects. Each of the categories is worth discussion on its own, but in this case we'll stick to the Structural patterns of Adapter, Facade, and Decorator.
He describes each of the patterns (no code in this one, just descriptions) and for each mentions some of the tools that the Zend Framework has to offer that match up. For example, the Adapter pattern is used in quite a few places in the framework including in the Zend_Db component for the connection types to different databases.