Craig Shoemaker has done is usual outstanding job with the latest installments of his Polymophic Podcast.  The last two shows have been a thought provoking interview with Miguel Castro.  In it they discuss design patterns that can be used to allow for greater flexibility and extensibility when building applications.  This is a topic that has interested me for a while now, especially patterns such as Dependency Injection which give the ability to define at run time the way that an application will act.  So take a listen and check out Miguel's article in Code Magazine (I admit I have only started reading it).  You may find new ways of thinking about you application designs.