While browsing the archives at thinkvitamin.com I came across an article by Robert Hoekman Jr called Deliverables That Work: Design Description Documents. In it he suggests combining use cases and wireframes or screenshot to make single design document. I generally provided detailed notes about the behaviour of the interface as part of my wireframes, however I like his suggest of using usecases.
One of the advantages of usecases is that they detail the exceptions to the normal flow. this is something that sometimes is missed when creating wireframes and results in the developer having to decide what to do as they come across issues.
The only issue I can see with this suggestion is that some times use cases can use multiple screens. In these instances I would suggest integrating the use case with a flow diagram and linking from the diagram to the appropriate pages.