Following up on their introduction to design patterns, the PHP Freaks have posted tutorials covering three of the more popular patterns - strategy/bridge, value object and singleton.

• Strategy and Bridge - The Strategy and Bridge patterns provide solutions to apply polymorphism in more flexible way than you can accomplish with only inheritance.
• Value Object - The Value Object pattern has, just like the Singleton, to do with referencing and instances. In a way, the Value Object is the opposite of the Singleton: it's goal is to ensure NOT to use the same instance, under certain conditions.
• Singleton and Singleton Registry - The Singleton pattern ensures that you are always dealing with the same, single instance, wherever in your application. The Registry pattern usually utilizes the Singleton pattern (hence "Singleton Registry") to make the same 'globalness' apply to objects who's classes weren’t necessarily designed to

Keep checking back to their tutorials section for more design pattern tutorials.