Introduction to the Observer Pattern by Matthew Cochran on Mar 08, 2009
This short (4:48) video demonstrates the essence of the Observer pattern.

Introduction to the Strategy Pattern by Matthew Cochran on Mar 08, 2009
This short (4:45) video demonstrates the essence of the Strategy pattern.

Introduction to the Command Pattern by Matthew Cochran on Mar 08, 2009
This short (3:05) video demonstrates the essence of the Command pattern.

Introduction to the Adapter Pattern by Matthew Cochran on Mar 08, 2009
This short (4:05) video demonstrates the essence of the Adapter pattern.