I'm working on creating documentation for a programming language and development environement. We're considering creating a wide variety of material including tutorials, reference material, inline documentation, videos, searchacle examples, et cetera.
There are two things I would love to hear from anybody:
1) Books/articles/anything you know of discussing design of documentation
2) Examples of awesome documentation that you know of. Even though I'm working on programming tools, I would love examples from any domain to get inspiration.