Saw a very good presentation by Ivar Jacobson called "all that jazz", he did an overview of Use Cases, Iterative development, architecture, and AOP. One of the continually interesting things about Dr. Jacobson's work is that he not only breaks down "how" things work, but also how they fit together.
AOP is particularly interesting from two angles:
1) Infrastructure code: security, exception handling and management, and logging
2) Ability to build and deploy an enterprise class app w/o the overhead of a full on J2EE app server