Mark Dalgarno recently published an excellent summary of a session presented by Steve Love at ACCU.
The talk offers a critique of the traditional doctrine that architectures should be layered. Instead, Love proposes a style based on designing to interfaces. That's music to my ears: it's exactly the approach we take in our new TDD with jMock2 course.
Love's presentation is available as a pdf. The first half consists of visuals alone; the second half combines the same visuals with notes.