Originally posted by Peer Reynders:
Domain Driven Design � Tackling Complexity in the Heart of Software isn't a patterns book but it discusses the Specification Pattern (PDF) (among others) at length.
DDD is an thoughtful, well-written book.
Originally posted by Svend Rost:
A problem with the GoF patterns is that 1) there are alot of them and 2) alot of them "look" alike (encapsulate change and delegate; for instance: Strategy vs. State). I asked this question becuase I was wondering if there were a smaller list.