Nice people keep sending me this link, so I'd better post it here.
Back when George Lucas and Steven Spielberg were first developing "Raiders of the Lost Ark", they had a brainstorming session with screenwriter Lawrence Kasdan. From what I've heard, those sessions were recorded and transcribed. I've seen xeroxes of those pages for years, but someone has finally posted all 125 pages online in .pdf format.
The link is here.
It's really great reading, especially because Lucas and Spielberg are so secretive about their process. You actually get a sense of their personalities from reading their quotes and an insight into how they both think.