Here are my notes from a Microsoft ArcReady seminar I went to in the middle of May. I went because I wanted to know more about building web applications that scale to many users. I definitely learned the basics of this, and found some references to other work as well.
At least one interesting thing that I learned was ProtoXAML, which is a way to take prototypes and make them seem a bit more flawed so that customers are more likely to give you good feedback. It was interesting to see this perspective, and might be helpful with some client interactions we have.